Midilibre.fr
Tous les blogs | Alerter le modérateur| Envoyer à un ami | Créer un Blog

16/01/2013

Cerveau, Comportement et Chimie

lu sur :

http://www.lemonde.fr/sante/article/2013/01/11/anorexie-et-hyperactivite-sont-liees-par-un-mecanisme-moleculaire-commun_1815804_1651302.html

Anorexie et hyperactivité sont liées par un mécanisme moléculaire commun

Le Monde.fr avec AFP | 11.01.2013 à 13h47

"L'anorexie et la cocaïne enclenchent la même voie moléculaire, ce qui tend à confirmer que l'anorexie est une addiction", explique Valérie Compan, qui a dirigé les travaux publiés dans la revue "Translational Psychiatry".

L'anorexie mentale, un trouble grave du comportement alimentaire, et l'hyperactivité physique sont liées par un mécanisme moléculaire commun, une découverte qui pourrait déboucher sur un traitement de cette pathologie qui touche principalement les adolescents, selon une récente étude.(*)

Alors qu'on pensait généralement que l'hyperactivité des anorexiques était intentionnelle et visait à perdre davantage de poids en brûlant des calories, une équipe mixte de chercheurs de l'Inserm et du CNRS et des universités (Montpellier-Nîmes) a découvert un mécanisme commun expliquant le lien entre les deux comportements.

RÉCOMPENSE

En utilisant des souris génétiquement modifiées capables de mimer une anorexie humaine, les chercheurs ont constaté qu'elles présentaient une anomalie moléculaire au niveau d'une région du cerveau impliquée dans la récompense.

Cette anomalie correspond à la "surexpression" (excès d'expression de gènes) du récepteur 5-HT4 à la sérotonine, un récepteur cellulaire qui contrôle également l'hyperactivité motrice chez les souris. "Nous avons identifié pour la première fois à notre connaissance, une voie moléculaire commune impliquée dans l'anorexie et l'hyperactivité", résume Valérie Compan qui a dirigé les travaux publiés à la fin de l'an dernier dans la revue Translational Psychiatry.

Les travaux ont également permis de confirmer l'existence de points communs entre l'anorexie et l'addiction. "L'anorexie et la cocaïne enclenchent la même voie moléculaire, ce qui tend à confirmer que l'anorexie est une addiction", ajoute Mme Compan.

ANOREXIE ET BOULIMIE

Les chercheurs ont également découvert que le récepteur pouvait devenirtotalement inactif et entraîner "une surconsommation d'aliments" qu'on retrouve notamment dans la boulimie. "Les perturbations affectant ce récepteur – tantôt trop actif et donc coupe faim, tantôt inactif – pourraient expliquer les oscillations entre anorexie et boulimie chez certains patients", estime la chercheuse qui espère que les travaux pourront être reproduits chez l'être humain.

"En l'absence totale de médicament pour traiter l'anorexie, ce récepteur pourrait représenter une cible thérapeutique efficace car en l'inactivant, les patients accepteraient à nouveau de se nourrir et en l'activant, ils pourraient modérer leurconsommation d'aliments" ajoute-t-elle.

-------------

(*) http://www.nature.com/tp/journal/v2/n12/full/tp2012131a.html

Original Article

Citation: Translational Psychiatry (2012) 2, e203; doi:10.1038/tp.2012.131
Published online 11 December 2012

The nucleus accumbens 5-HTR4-CART pathway ties anorexia to hyperactivity

A Jean1,2,3,4,9, L Laurent1,2,3,9, J Bockaert1,2,3, Y Charnay5, N Dusticier6, A Nieoullon6, M Barrot7, R Neve8 and V Compan1,2,3,4

  1. 1Institut de Génomique Fonctionnelle, Montpellier, France
  2. 2INSERM, U661, Montpellier, France
  3. 3Universités de Montpellier 1 and 2, UMR-5203, Montpellier, France
  4. 4Université de Nîmes, Nîmes, France
  5. 5Hôpitaux Universitaires de Genève, Division de Neuropsychiatrie, Chêne-Bourg, Switzerland
  6. 6Université d’Aix-Marseille, Marseille, France
  7. 7Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
  8. 8Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA

Correspondence: Dr V Compan, Neurobiology, Institut de Génomique Fonctionnelle, 141, rue de la Cardonille, Montpellier 34094, France. E-mail: Valerie.Compan@igf.cnrs.fr

9Authors equally contribute to this study.

Received 17 August 2012; Revised 6 October 2012; Accepted 10 October 2012

Top

Abstract

In mental diseases, the brain does not systematically adjust motor activity to feeding. Probably, the most outlined example is the association between hyperactivity and anorexia in Anorexia nervosa. The neural underpinnings of this ‘paradox’, however, are poorly elucidated. Although anorexia and hyperactivity prevail over self-preservation, both symptoms rarely exist independently, suggesting commonalities in neural pathways, most likely in the reward system. We previously discovered an addictive molecular facet of anorexia, involving production, in the nucleus accumbens (NAc), of the same transcripts stimulated in response to cocaine and amphetamine (CART) upon stimulation of the 5-HT4 receptors (5-HTR4) or MDMA (ecstasy). Here, we tested whether this pathway predisposes not only to anorexia but also to hyperactivity. Following food restriction, mice are expected to overeat. However, selecting hyperactive and addiction-related animal models, we observed that mice lacking 5-HTR1B self-imposed food restriction after deprivation and still displayed anorexia and hyperactivity after ecstasy. Decryption of the mechanisms showed a gain-of-function of 5-HTR4 in the absence of 5-HTR1B, associated with CART surplus in the NAc and not in other brain areas. NAc-5-HTR4 overexpression upregulated NAc-CART, provoked anorexia and hyperactivity. NAc-5-HTR4 knockdown or blockade reduced ecstasy-induced hyperactivity. Finally, NAc-CART knockdown suppressed hyperactivity upon stimulation of the NAc-5-HTR4. Additionally, inactivating NAc-5-HTR4 suppressed ecstasy’s preference, strengthening the rewarding facet of anorexia. In conclusion, the NAc-5-HTR4/CART pathway establishes a ‘tight-junction’ between anorexia and hyperactivity, suggesting the existence of a primary functional unit susceptible to limit overeating associated with resting following homeostasis rules.

Keywords: 

feeding; 5-HT1B; 5-HT4; knockout; locomotion; reward

Top

Introduction

In mental diseases (for example, depression, anxiety, eating disorders), the brain does not systematically adjust energy expenditures to intakes, as highlighted by the ‘paradoxical’ association between restrictive diet and motor hyperactivity in Anorexia nervosa.123 Here, we set out to study potential neural underpinnings of this apparent homeostatic failure. We reasoned that if at least one single molecular pathway triggers both anorexia and motor hyperactivity, its abnormal activation could prevail over homeostasis rules. In this situation, interpreting motor hyperactivity as an ‘intention’ of patients with anorexia could be challenged because their motor hyperactivity would be anorexia-dependent. In contrast, if two parallel and different pathways trigger anorexia on one hand, and motor hyperactivity on the other hand, a complex coincidence of two parallel impairments in both the feeding and motor neural networks could be in cause.

Among the cumulative neural events related to anorexia, as in most eating disorders, altered 5-HT volume transmission4 is at the forefront of investigations.5 With exceptions, regardless stimulation of 5-HT1A and 5-HT2Breceptors (5-HTR1A, 5-HTR2B) in the hypothalamus,6 increased activity of 5-HT transmission in brain following treatments classically reduces feeding and body weight.7 For instance, the 3,4-N-methylenedioxymethamphetamine (MDMA, ecstasy) diminishes feeding in rodents and humans, and enhances motor hyperactivity.891011

The hypothalamus appears central in regulating feeding behavior,12 but motivation disorders related to self-imposed food restriction despite energy demand (anorexia) may involve disturbances in the nucleus accumbens (NAc),7,1314 a brain structure involved in reward and feeding.15161718 Considering the ability of 5-HT4 receptors (5-HTR4) knockout (KO) mice to better resist stress-induced anorexia, we detected a first example of an addictive molecular facet of anorexia.1419 Indeed, stimulating NAc-5-HTR4, as MDMA, provokes anorexia only if production of the same transcripts stimulated in response to cocaine and amphetamine (CART) is increased in the NAc.14

We investigated, here, whether the NAc-5-HTR4/CART molecular pathway triggers not only anorexia but also motor hyperactivity. To address this possibility, we used (i) an addiction- and hyperactive-related animal model: the 5-HTR1B KO (KO1B) mice, (ii) the ability of MDMA to mimic both anorexia and hyperactivity and (iii) siRNA- and viral-mediated knockdown and surplus strategies combined to molecular and behavioral techniques.

Top

Methods

Animals

Male KO1B, KO4 and control mice (WT1B, WT4) from heterozygous breeding (129/SvTer)1920 were housed with food and water available ad libitum.14 Male WT 129/SvPas mice were used when KO mice were not required. All experiments were performed on mice aged of 4–6 months, except a set, aged of 2 months (Figures 1a and b), following the Guide for Care and Use of Laboratory Animals(authorization n° 21CAE011) (see Supplementary Information).

 
Figure 1.
Figure 1 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

Anorexia-like symptoms in KO1B mice are treated with RS39604, a 5-HTR4 antagonist. (ac) Total food intake of WT1B and KO1B mice following (ab) 3 days of diet (−20%), over 24-h after NaCl or RS39604 (0.5mg/kg) and (c) 24h of 100% food deprivation, over 1h after NaCl, MDMA (10mgkg−1, RS39604 alone, or combined with MDMA. (d-f) Total distance traveled (de) every 5min (f) over 110-min after MDMA combined with RS39604 or not compared with NaCl. Data are means±s.e.m.; n=7–11 per group of mice treated with i.p. administration of each compound. *P<0.05, **P<0.01; §P<0.05, §§P<0.01, §§§P<0.001;$P<0.05, $$$P<0.001 compared with WT1B, NaCl and MDMA, respectively; #P<0.05, ##P<0.01 genotype and treatment interaction.

Full figure and legend (110K)
 

Surgery

As described in detail,14 a sterile 26-gauge stainless steel guide was unilaterally implanted in the left shell NAc for infusing 1μl of each compound in freely moving mice (1μl/min). The localization of the injection site was assessed in each mouse (see Supplementary Information).

 

Pharmacological and nucleic acid treatments in freely moving mice

As established,111421 MDMA (10mgkg−1, Sigma, L'Isle d'Abeau Chesnes, Saint-Quentin-Fallavier, France) and selective dose of 5-HTR4 antagonist, RS39604 (0.5mgkg−1, Tocris, Ellisville, USA) were dissolved in NaCl (9%) before acute intraperitoneal (i.p.) administration. The 5-HTR4 agonist BIMU8 (Tocris, Ellisville, USA) and RS39604 was injected in the NAc at selective dose (4 × 10−4μgμl−1). Acute injection in the NAc of (i) double-stranded siRNA-5-HTR4(si5-HTR4), siCART provoked 5-HTR4 and CART downregulation compared with siRNA controls (siCt: 0.05μgμl−1), respectively; and of (ii) viral vector of mHtr4 gene (HSV-5-HTR4; 107 infectious units per ml, 1μlmin−1), an overexpression of 5-HTR4 compared with HSV-LacZ construct (see Supplementary Information).

 

Biochemical analyses

As described,22 the levels of 5-HT and 5-HIAA were evaluated in brain tissue samples containing the NAc (+1.6mm), striatum (+1.0mm), dorsal hippocampus (−2.2mm) and amygdala (−3.2mm from the bregma)23 of WT4 and KO4 mice sacrificed 5min after the end of the open-field session. As reported in detail,14,19 receptor autoradiography was performed using (125I)SB207710 and (3H)GR113808, two specific 5-HTR4 antagonists (see Supplementary Information).

 

Quantitative Real-Time PCR

Mice were sacrificed 3-h after the different treatments and NAc (2 × 1.2mm3) and hypothalamus (3.9mm3) were micro-dissected from 1mm-thick sections to treat total mRNA and treat complementary DNA in reactions containing CART or 5-HTR4 primers, as described in detail.1424

 

Activity

Naive or feeding-tested mice were tested in the open-field19 after i.p. administration of NaCl or MDMA combined with (i) i.p. administration of RS39604 in KO1B, KO4, WT1B and WT4 mice and intra-accumbal infusion of (ii) si5-HTR4,RS39604, siCt (or NaCl) as controls in WT 129Sv/Pas mice and (iii) HSV-5-HTR4, BIMU8 combined or not with siCART, compared with controls (NaCl, HSV-LacZ, siCt) in WT 129Sv/Pas mice. Ten min after RS39604 injection, 3h after injection of the siRNAs or BIMU8, or 1 day after viral infection, the traveled path length was monitored.19

 

Feeding tests

Classic feeding paradigms1119 were used in fed mice or, following (i) 100% food deprivation for 24h or (ii) 20% food-restriction for 3 consecutive days. Four days before the experiments, mice were isolated in metabolic cages for baseline period with ad libitum access to food (pellet form, 16.5% crude proteins, 3.6%crude fat, 4.6% crude fibers, 5.2% ash). Food-deprived WT1B and KO1B mice were treated with i.p. administration of NaCl or RS39604 combined or not with MDMA. WT129Sv/Pas mice received acute infusion of HSV-5-HTR4 or HSV-LacZ in the NAc and were 20% food-deprived for 3 days. The amount of food consumed (not include the spillage) was measured with 1mg precision.

 

Place conditioning paradigm

An unbiased place conditioning protocol was adapted.25 Mice received i.p. administration of NaCl, MDMA combined or not with RS39604, or injection in the NAc of NaCl or RS39604, 30min before being confined to a single conditioning zone on alternate conditioning days. A preference score is the difference between times spent by each mouse in the MDMA-, NaCl-, RS39604-, or MDMA plus RS39604-paired zone during the preconditioning and testing phases (see Supplementary Information).

 

Statistical analysis

Data obtained in multiple sessions over time (food intake, locomotion) were analyzed using repeated measures analysis of variance (STATVIEW 5 software, SAS Institute Inc., San Francisco, CA, USA). When effects of independent variables (treatment, genotype, time), or interactions were significant, one-way analysis of variance (treatment, time or genotype) analyses were performed. For multiple comparisons, the Scheffé F-test was used. Differences with P<0.05 were considered significant.

 
Top

Results

KO1B self-imposed food restriction following restriction and displayed hyperactivity: Anorexia-like symptoms still observed after MDMA

Considering the influence of 5-HT in the potential rewarding facet of anorexia,14we tested whether an animal model predisposes to abuse of cocaine, and to be hyperactive persists to self-restrict following food restriction. Young KO1B and WT1B mice (2 months) were then selected2627 and deprived of 20% of their normal food rations for 3 days in their home cages (means±s.e.m. of normal food ration for 24h expressed in g. in WT1B: 4.80±0.09 vs KO1B: 4.82±0.16). When food was reintroduced and available ad libitum after the diet period, WT1Bmice were eating more than their normal meal size (Figure 1a). This rebound in food intake was reduced in KO1B mice that even ate less than their predeprivation food ration after 3 days ad libitum (Figure 1a). Moreover, KO1Bmice did display increased locomotion compared with saline-injected WT1B mice (Figures 1d and f), as reported.2628

Following MDMA in KO1B mice, anorexia (Figure 1c), and hyperactivity although reduced (Figures 1e and f), are still observed, consistently with a previous study using a 5-HTR1B antagonist (GR127935).11

The absence of 5-HTR1B then predisposes to anorexia-like symptoms in challenge situations. We next tested whether this predisposition requires 5-HTR4.

Inactivating 5-HTR4 in KO1B mice suppressed their anorexia and hyperactivity

Selective inactivation of 5-HTR414 in food-restricted KO1B mice restores adaptive feeding and motor responses because the mutant did not self-restrict (Figure 1b) and were not hyperactive anymore (Figures 1d and f). Inactivating 5-HTR4suppressed anorexia (Figure 1c) and hyperactivity (Figures 1e and f) induced by MDMA in KO1B compared with NaCl-treated KO1B mice. Identical dose of antagonist only reduced both effects in WT1B mice (Figures 1c–f), suggesting a gain-of-function of 5-HTR4 owing the absence of 5-HTR1B. To ensure this issue, we first assessed whether the gene defective-mutation of 5-HTR4 reduce hyperactivity induced by novelty and MDMA. This is the observed effect (Supplementary Figure S1). We then evaluated the density of 5-HTR4 sites and mRNA in the brain of KO1B mice.

 

Only the NAc of KO1B mice over-expressed both 5-HTR4 and CART whereas its hypothalamus over-expressed 5-HTR4 but down-expressed CART

Among brain areas examined (Supplementary Table S1), 5-HTR4 density (Figure 2a) and mRNA content (Figure 2b) were higher in the NAc and hypothalamus of KO1B compared with WT1B mice. The levels of CART mRNA were higher in the NAc and weaker in the hypothalamus of KO1B compared with WT1B mice (Figures 2c and d). Because CART in both the NAc and hypothalamus decreases feeding,1429 its opposite changes could underlie the adequate feeding behavior of KO1B mice in baseline conditions.1130 Accordingly, the ability of KO1B mice to self-restrict of food might depend on excessive NAc-5-HTR4. We next focused on the NAc because additionally, marked increases in 5-HT metabolism were not detected in the NAc of KO4 mice following the open-field session (Supplementary Table S2). To avoid bias of adaptive changes in KO mice and determine whether a 5-HTR4 surplus within the NAc triggers both anorexia and hyperactivity, mHtr4 gene (HSV-5-HTR4) was transferred in the NAc of WT mice.

 
Figure 2.
Figure 2 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

KO1B mice over-expressed 5-HTR4 and CART in the NAc. (a) The density of 5-HTR4 binding site ((3H)GR113808) of KO1B compared with WT1B mice following analyses of 3–6 brain frontal sections per structure level and per mouse (n=5). (b) 5-HTR4 and (c) CART mRNA content in the NAc and hypothalamus (Hyp) of KO1B (n=6) and WT1B mice (n=7). (dIn situ hybridization of CART mRNA (scale bar: NAc, 100μm; Hyp, 1mm; arrows point to changes). Data are means±s.e.m.; and P<0.05 difference between the NAc and Hyp in either WT1B or KO1B mice;*P<0.05, **P<0.01 compared with WT1B.

Full figure and legend (157K)
 

Overexpression of 5-HTR4 in the NAc ties anorexia to hyperactivity

Injecting HSV-5-HTR4 in the NAc of WT mice increased the density of NAc-5-HTR4at 54-h postinjection (Figure 3a). The NAc-5-HTR4 mRNA content was still higher at 72h than in control mice (HSV-LacZ), with the highest level observed at 30-h postinjection (Figure 3b). Consistently, CART mRNA content at 72-h postinjection was increased in the NAc (Figure 3c) and unchanged in the hypothalamus (Figure 3c) following injection of HSV-5-HTR4 in the NAc, compared with controls. Stimulating NAc-5-HTR4 also increases CART mRNA content in the NAc but not in the hypothalamus.14

Figure 3.
Figure 3 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

Overexpression of 5-HTR4 in the NAc ties anorexia to hyperactivity in WT mice. (a) Increased density of NAc-5-HTR4 binding site ((125I)SB207710) in the NAc (1) but not in nearness structure (2: ventral pallidum) observed on transverse brain sections from mice infused in the NAc with HSV-5HTR4 compared with control (HSV-LacZ) and sacrificed 54-h postinfusion. Circles highlight changes and delineate the injection site in a brain section stained with hematoxylin (right upper panel), indicating an absence of damage tissue. (b) NAc-5-HTR4 mRNA content increased after infusion, in the NAc, of HSV-5-HTR4 (n=8 mice for each time point for both conditions). (c) NAc- and Hyp-CART mRNA content 72h after injection of HSV-5-HTR4 or HSV-LacZ. (df) Total food intake in (d) fed and (f) food-deprived (3 days, 20%) mice (d) 24h and (f) 3 days after infusion, in the NAc, of HSV-5-HTR4 (n=6) or HSV-LacZ (n=5). (e) Total distance traveled. Data are means±s.e.m.;§P<0.05, §§P<0.01, §§§P<0.001 compared to HSV-LacZ; &P<0.05 differences between the NAc and hypothalamus; ###P<0.001 interaction between time and treatment.

Full figure and legend (157K)
 

The feeding and motor behaviors were then analyzed. At 24-h postinjection, overexpressing NAc-5-HTR4 decreased feeding (35%Figure 3d) and enhanced motor activity (148%Figure 3e). HSV-5-HTR4 mice did further self-restrict after restriction compared with controls (Figure 3f), mimicking feeding responses of KO1B mice, following 20% of their normal food rations for 3 days.

Subsequently, NAc-5-HTR4 surplus increased CART, decreased feeding and increased motor activity. To circumvent the ectopic expression after viral vector injection, potential conclusion was ensured using pharmacological and RNA interference approaches, as we established.14

In the NAc, stimulation of 5-HTR4 increases motor activity, and their blockade reduces hyperactivity

The distance covered in the open-field is enhanced following stimulation of NAc-5-HTR4 with a specific dose of BIMU8, an agonist (198%), and unchanged following their specific blockade with antagonist or RNA interference (si5-HTR4) infused in the NAc (Figures 4a and b). In contrast, antagonism or knockdown of NAc-5-HTR4 reduced hyperactivity induced by i.p. administration of MDMA (Figure 4a).

 
Figure 4.
Figure 4 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

Motor hyperactivity induced by stimulation of NAc-5-HTR4 requires CART. (a) Total distance traveled over 110min after i.p. administration of NaCl or MDMA plus an intra-accumbal infusion of control solution (NaCl or si5-HTR4 control: siCt), si5-HTR4, 5-HTR4 antagonist (RS39604) and (b) of WT mice after an intra-accumbal infusion of controls, 5-HTR4 agonist (BIMU8), siCART or BIMU8 plus siCART. Data are means±s.e.m.; n=5–10 mice per each group, treated with MDMA (10mgKg−1), siRNA (0.05μgμl−1), viral vector (107 infectious units per ml), RS39064 or BIMU8 (4 × 10−4μgμl−1). §§P<0.01, $$P<0.01,&&&P<0.001 compared to controls, MDMA and BIMU8, respectively.

Full figure and legend (44K)
 

CART knockdown in the NAc inhibits stimulating NAc-5-HTR4-induced motor hyperactivity

We next examined whether CART in the NAc mediates the motor effects of BIMU8, a 5-HTR4 agonist. Blocking CART with RNA interference (siCART) in the NAc suppressed the motor hyperactivity induced by stimulation of 5-HTR4 (Figure 4b).

We finally tested whether MDMA’s preference requires 5-HTR4 because a rewarding effect could prevail over self-preservation.

Inactivating 5-HTR4 suppressed MDMA’s preference in WT and reduced it in KO1B mice

Using the conditioned place preference test, we found that The KO1B mice displayed a higher preference for MDMA than WT1B mice (Figure 5a), which is reduced after i.p. administration of a 5-HTR4 antagonist (Figure 5a). An absence of preference for MDMA is further shown when 5-HTR4 is locally inactivated in the NAc of adult WT4 mice (Figure 5b).

 
Figure 5.
Figure 5 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

MDMA’s preference involves 5-HTR4 in an unbiased conditioned place preference test. (a) Score preference in WT1B and KO1B mice treated with i.p. administration of NaCl, MDMA (10mgkg−1), combined or not with RS39604 (0.5mgkg−1) and (b) in WT mice treated with i.p. administration of NaCl or MDMA (10mgkg−1) plus intra-accumbal infusion of NaCl or RS39604 (4 × 10−4μgμl−1). Data are means±s.e.m.; n=7–9 mice per group. *P<0.05 compared to WT1B§P<0.05,§§P<0.01 compared with NaCl; $P<0.05, $$P<0.01 compared with MDMA.

Full figure and legend (55K)
 
Top

Discussion

Over the last ten decades, parallel neural systems have been described to control feeding and motor behaviors. Here, we found a first example of a molecular signal foul-up between motor hyperactivity and anorexia, providing a common pathway of control. This would lead us to reconsider the belief that patients with anorexia nervosa intend to accelerate their weight loss with over-exercise3313233 because hyperactivity could be more inevitable than deliberate.

These findings strengthen the addictive facet of restrictive diet, now also observed in mice, dispossessed of 5-HTR1B and/or endowed of a NAc-5-HTR4surplus because they self-restrict despite an upstream ‘starter’ period of restrictive diet, believed to trigger ‘spiral’ restrictions in humans.34

Animal models of anorexia-like symptoms predisposition, identified herein, mimic the activity-based anorexia rat model,35 and are to the best of our knowledge, unique. It is noteworthy to observe that KO1B mice persist to self-restrict their intake of food. Excluding adaptive mechanisms, KO1B mice would be expected to consume a higher amount of food because stimulating 5-HTR1Bdecreases feeding.1136 This phenotype is apparently not related to the reduced activity of 5-HTR2C in KO1B mice37 because stimulating 5-HTR2C decreases feeding.38 In contrast, present results showed a gain-of-function of 5-HTR4, consistent with the inhibitory influence of 5-HTR4 on feeding.1419 Also, inactivating 5-HTR4 suppressed motor hyperactivity in KO1B mice, consistently with the weaker efficacy of MDMA to enhance locomotion in KO4 and 5-HTR4antagonist-treated WT mice.

The surplus of 5-HTR4 in KO1B mice further suggests a negative 5-HTR1B control of 5-HTR4 accordant with series of results; (i) The decreased levels of NAc-5-HT in KO1B mice39 because lesion of 5-HT neurons, though in rats, upregulates 5-HTR4 in brain areas including the NAc;40 (ii) The 5-HTR1B and 5-HTR4 location does not overlap (for example. in the striatum,4041 on 5-HT neurons244243) likely related to their common binding to p11;4445 (iii) KO1B mice are hyperactive and less ‘anxious’46 while KO4 mice are hypoactive and more ‘anxious’ under stress.1947

Molecular events for driving self-restriction and motor hyperactivity are detected in the NAc. The NAc-5-HTR4 surplus induced sustained anorexia and motor hyperactivity, mimicking the molecular and behavioral phenotypes of KO1B mice (NAc-5-HTR4/CART surplus, anorexia, hyperactivity). Similarly, stimulation of NAc-5-HTR4 decreases feeding14 and increases locomotion.

As difference in feeding responses to activation of 5-HTR subtypes, stimulation of 5-HTR1B, 5-HTR2C, 5-HTR1-7 and 5-HTR6 in the NAc did not change locomotion in basal conditions, however, in rats (Supplementary Figure S2).484950 Likewise, blocking or silencing NAc-5-HTR4 did not change locomotion but suppressed hyperactivity induced by MDMA, in tune with the effect of the whole blockade of 5-HTR1B, 5-HTR2B and 5-HTR2C.2851525354 In rats, inactivating NAc-5-HTR4did not however, alter hyperactivity after MDMA,50 suggesting differences between doses and species.5511

To the end, stimulating NAc-5-HTR4 in mice not only triggers anorexia but also hyperactivity, consistent with opposite changes in feeding and locomotion detected only in KO4 mice, compared with other 5-HTR KO mice (Supplementary Figure S2).

The present study extends observations at a molecular level. Ectopic (viralmHtr4 gene) or ‘physiological’ surplus of NAc-5-HTR4 in KO1B mice upregulates NAc-CART, as observed following stimulation of NAc-5-HTR4.14 A final experiment in our series bore out our hypothesis because NAc-CART knockdown suppressed not only anorexia14 but also motor hyperactivity induced by NAc-5-HTR4 stimulation. In addition, locomotion is unchanged following CART peptide56or siCART injection in the NAc. Identifying the cellular origin of this action would require long investigations. Nonetheless, NAc-neurons containing GABA projecting to the lateral hypothalamus express CART14575859 and might also express 5-HTR4 (Supplementary Figure S2).24404358 Injecting si5-HTR4 in the NAc decreased the density of 5-HTR4 not only in the NAc but also in the lateral hypothalamus (−14%, not illustrated). The 5-HTR4 located on these neurons may influence feeding and locomotion (Supplementary Figure S2) because the lateral hypothalamus, in relation to the NAc, controls feeding and its stimulation enhances locomotion in the activity-based rat model for anorexia nervosa.1560,616263 Colocalization of 5-HTR4/CART is more conceivable than in two different neuronal populations, considering the 5-HTR4 control of CART within the NAc via a cAMP/PKA signaling pathway.14 Interestingly, it appears that 5-HT receptors expressed in the different subnuclei of the hypothalamus (arcuate nucleus: 5-HTR1B, 5-HTR2C) may provoke an anorexia associated or not with different changes in locomotion, as induced by fenfluramine6465 that increase,51decrease6667 or does not modify locomotion68 while, 5-HTR4 likely located on the afferent neurons of the NAc to the lateral hypothalamus may provoke an anorexia associated with motor hyperactivity.

Finally, the present study suggests that activation of the NAc-5-HTR4 promotes a rewarding effect because (i) mice with NAc-5-HTR4 surplus limit their food intake despite energy requirements; (ii) inactivating NAc-5-HTR4 can reduce and even suppress the preference for MDMA, as also observed in 5-HTR2B KO mice.69Chronic stimulation may desensitize 5-HTR470 and has been excluded from our subtasks. Nonetheless, increased cAMP production in the NAc71 upon stimulation of the 5-HTR4 in freely moving mice14 could trigger addiction.

In conclusion, motor hyperactivity is anorexia-dependent upon activation of the NAc-5-HTR4/CART pathway. Probably, a rewarding effect associated with energy expenditure (anorexia/hyperactivity) may facilitate to limit excessive intakes (overeating/resting). Present and previous findings6146472 bring out at least two modes of action of 5-HT to regulate feeding. In baseline conditions, feeding may be regulated via the hypothalamic 5-HTR2C/CART pathway but, when motivation comes into play, the NAc-5-HTR4/5-HTR1B/CART pathway might prevail over the autonomic nervous control of feeding because NAc-5-HTR4/CART surplus makes the brain ‘silent’ to energy loss. Finally, it is conceivable that an anorectic-rewarding pathway of the NAc predisposes animals to a possible dependence on restrictive diet and hyperactivity, two hallmarks of anorexia nervosa.

Top

Conflict of interest

Authors declare no conflict of interest.

Top

References

  1. Beumont PJ, Arthur B, Russell JD, Touyz SW. Excessive physical activity in dieting disorder patients: proposals for a supervised exercise program. Int J Eat Disord 1994; 15: 21–36. | Article | PubMed |
  2. Davis C. Eating disorders and hyperactivity: a psychobiological perspective.Can J Psychiatry 1997; 42: 168–175. | PubMed | ISI |
  3. Casper RC. The 'drive for activity' and "restlessness" in anorexia nervosa: potential pathways. J Affect Disord 2006; 92: 99–107. | Article | PubMed |
  4. Descarries L, Beaudet A, Watkins KC. Serotonin nerve terminals in adult rat neocortex. Brain Res 1975; 100: 563–588. | Article | PubMed | ISI | CAS |
  5. Kumar KK, Tung S, Iqbal J. Bone loss in anorexia nervosa: leptin, serotonin, and the sympathetic nervous system. Ann N Y Acad Sci 2010;1211: 51–65. | Article | PubMed |
  6. Yadav VK, Oury F, Suda N, Liu ZW, Gao XB, Confavreux C et al. A serotonin-dependent mechanism explains the leptin regulation of bone mass, appetite, and energy expenditure. Cell 2009; 138: 976–989. | Article | PubMed | ISI | CAS |
  7. Compan V, Laurent L, Jean A, Macary C, Bockaert J, Dumuis A. Serotonin signaling in eating disorders. WIREs Membrane Transport and Signaling (invited by G. Knudsen) 2012; 1: 715–719. | Article |
  8. Rochester JA, Kirchner JT. Ecstasy (3,4-methylenedioxymethamphetamine): history, neurochemistry, and toxicology. J Am Board Fam Pract 1999; 12: 137–142. | PubMed |
  9. Geyer MAC, C.W. Behavioral pharmacology of ring-substituted amphetamine analogs. Amphetamine and its AnalogsIn: Cho AR, Segal OS (eds). Academic Press: New York, 1994 pp 177–201.
  10. Frith CH, Chang LW, Lattin DL, Walls RC, Hamm J, Doblin R. Toxicity of methylenedioxymethamphetamine (MDMA) in the dog and the rat. Fundam Appl Toxicol 1987; 9: 110–119. | Article | PubMed | ISI | CAS |
  11. Conductier G, Crosson C, Hen R, Bockaert J, Compan V. 3,4-N-methlenedioxymethamphetamine-induced hypophagia is maintained in 5-HT1B receptor knockout mice, but suppressed by the 5-HT2C receptor antagonist RS102221. Neuropsychopharmacology 2005; 30: 1056–1063. | Article | PubMed | ISI | CAS |
  12. Schwartz MW, Woods SC, Porte D, Seeley RJ, Baskin DG. Central nervous system control of food intake. Nature 2000; 404: 661–671. | Article | PubMed | ISI | CAS |
  13. Compan V. Serotonin receptors in neurobiology. do limits of neuronal plasticity represent an opportunity for mental diseases, such as addiction to food and illegal drugs? use and utilities of serotonin receptor knock-out mice. CRC press, New frontiers in Neurosciences: Boca Raton, Florida, 2007 pp 157–180.
  14. Jean A, Conductier G, Manrique C, Bouras C, Berta P, Hen R et al. Anorexia induced by activation of serotonin 5-HT4 receptors is mediated by increases in CART in the nucleus accumbens. Proc Natl Acad Sci U S A2007; 104: 16335–16340. | Article | PubMed |
  15. Stratford TR, Kelley AE. GABA in the nucleus accumbens shell participates in the central regulation of feeding behavior. J Neurosci 1997; 17: 4434–4440. | PubMed | ISI | CAS |
  16. Bassareo V, Di Chiara G. Modulation of feeding-induced activation of mesolimbic dopamine transmission by appetitive stimuli and its relation to motivational state. Eur J Neurosci 1999; 11: 4389–4397. | Article | PubMed | ISI | CAS |
  17. Reynolds SM, Berridge KC. Fear and feeding in the nucleus accumbens shell: rostrocaudal segregation of GABA-elicited defensive behavior versus eating behavior. J Neurosci 2001; 21: 3261–3270. | PubMed | CAS |
  18. Hoebel BG. Brain neurotransmitters in food and drug reward. Am J Clin Nutr 1985; 42(5 Suppl): 1133–1150. | PubMed | CAS |
  19. Compan V, Zhou M, Grailhe R, Gazzara RA, Martin R, Gingrich J et al. Attenuated response to stress and novelty and hypersensitivity to seizures in 5-HT4 receptor knock-out mice. J Neurosci 2004; 24: 412–419. | Article | PubMed | ISI | CAS |
  20. Saudou F, Amara DA, Dierich A, LeMeur M, Ramboz S, Segu L et al. Enhanced aggressive behavior in mice lacking 5-HT1B receptor. Science1994; 265: 1875–1878. | Article | PubMed | ISI | CAS |
  21. Lucas G, Compan V, Charnay Y, Neve RL, Nestler EJ, Bockaert J et al. Frontocortical 5-HT4 receptors exert positive feedback on serotonergic activity: viral transfections, subacute and chronic treatments with 5-HT4 agonists. Biol Psychiatry 2005; 57: 918–925. | Article | PubMed | ISI | CAS |
  22. Dusticier N, Nieoullon A. Comparative analysis of the effects of in vivoelectrical stimulation of the frontal cortex and g-butyrolactone administration on dopamine and dihydroxyphenylacetic acid (DOPAC) striatal contents in the rat. Neurochem Int 1987; 10: 275–280. | Article | PubMed |
  23. Franklin KBJ, Paxinos G. The mouse brain in stereotaxic coodinates. Academic press: San Diego, 1997.
  24. Conductier G, Dusticier N, Lucas G, Cote F, Debonnel G, Daszuta A et al. Adaptive changes in serotonin neurons of the raphe nuclei in 5-HT(4) receptor knock-out mouse. Eur J Neurosci 2006; 24: 1053–1062. | Article | PubMed |
  25. Robledo P, Balerio G, Berrendero F, Maldonado R. Study of the behavioural responses related to the potential addictive properties of MDMA in mice.Naunyn Schmiedebergs Arch Pharmacol 2004; 369: 338–349. | Article | PubMed |
  26. Brunner D, Buhot MC, Hen R, Hofer M. Anxiety, motor activation, and maternal-infant interactions in 5HT1B knockout mice. Behav Neurosci1999; 113: 587–601. | Article | PubMed | ISI | CAS |
  27. Rocha BA, Fumagalli F, Gainetdinov RR, Jones SR, Ator R, Giros B et al. Cocaine self-administration in dopamine-transporter knockout mice. Nat Neurosci 1998; 1: 132–137. | Article | PubMed | ISI | CAS |
  28. Scearce-Levie K, Viswanathan SS, Hen R. Locomotor response to MDMA is attenuated in knockout mice lacking the 5-HT1B receptor.Psychopharmacology (Berl) 1999; 141: 154–161. | Article | PubMed | CAS |
  29. Kristensen P, Judge ME, Thim L, Ribel U, Christjansen KN, Wulff BS et al. Hypothalamic CART is a new anorectic peptide regulated by leptin. Nature1998; 393: 72–76. | Article | PubMed | ISI | CAS |
  30. Lucas JJ, Yamamoto A, Scearce-Levie K, Saudou F, Hen R. Absence of fenfluramine-induced anorexia and reduced c-Fos induction in the hypothalamus and central amygdaloid complex of serotonin 1B receptor knock-out mice. J Neurosci 1998; 18: 5537–5544. | PubMed | CAS |
  31. Holtkamp K, Hebebrand J, Herpertz-Dahlmann B. The contribution of anxiety and food restriction on physical activity levels in acute anorexia nervosa. Int J Eat Disord 2004; 36: 163–171. | Article | PubMed |
  32. Konttinen H, Silventoinen K, Sarlio-Lahteenkorva S, Mannisto S, Haukkala A. Emotional eating and physical activity self-efficacy as pathways in the association between depressive symptoms and adiposity indicators. Am J Clin Nutr 2010; 92: 1031–1039. | Article | PubMed |
  33. Steanovv TS, Vekova AM, Kurktschiev DP, Temelkova-Kurktschiev TS. Relationship of physical activity and eating behaviour with obesity and type 2 diabetes mellitus: Sofia Lifestyle (SLS) study. Folia Med (Plovdiv) 2011;53: 11–18. | Article | PubMed |
  34. Dignon A, Beardsmore A, Spain S, Kuan A. 'Why I won't eat': patient testimony from 15 anorexics concerning the causes of their disorder. J Health Psychol 2006; 11: 942–956. | Article | PubMed |
  35. van Kuyck K, Casteels C, Vermaelen P, Bormans G, Nuttin B, Van Laere K. Motor- and food-related metabolic cerebral changes in the activity-based rat model for anorexia nervosa: a voxel-based microPET study.Neuroimage 2007; 35: 214–221. | Article | PubMed |
  36. Vickers SP, Dourish CT, Kennett GA. Evidence that hypophagia induced by d-fenfluramine and d-norfenfluramine in the rat is mediated by 5-HT2C receptors. Neuropharmacology 2001; 41: 200–209. | Article | PubMed | ISI |
  37. Clifton PG, Lee MD, Somerville EM, Kennett GA, Dourish CT. 5-HT1B receptor knockout mice show a compensatory reduction in 5-HT2C receptor function. Eur J Neurosci 2003; 17: 185–190. | Article | PubMed |
  38. Kennett GA, Curzon G. Evidence that hypophagia induced by mCPP and TFMPP requires 5-HT1C and 5-HT1B receptors; hypophagia induced by RU 24969 only requires 5-HT1B receptors. Psychopharmacology (Berl) 1988;96: 93–100. | Article | PubMed |
  39. Ase AR, Reader TA, Hen R, Riad M, Descarries L.. Altered serotonin and dopamine metabolism in the CNS of serotonin 5-HT(1A) or 5-HT(1B) receptor knockout mice. J Neurochem 2000; 75: 2415–2426. | Article | PubMed | ISI | CAS |
  40. Compan V, Daszuta A, Salin P, Sebben M, Bockaert J, Dumuis A. Lesion study of the distribution of serotonin 5-HT4 receptors in rat basal ganglia and hippocampus. Eur J Neurosci 1996; 8: 2591–2598. | Article | PubMed |
  41. Compan V, Segu L, Buhot MC, Daszuta A. Selective increases in serotonin 5-HT1B/1D and 5-HT2A/2C binding sites in adult rat basal ganglia following lesions of serotonergic neurons. Brain Res 1998; 793: 103–111. | Article | PubMed | ISI | CAS |
  42. Doucet E, Pohl M, Fattaccini CM, Adrien J, Mestikawy SE, Hamon M. In situ hybridization evidence for the synthesis of 5-HT1B receptor in serotoninergic neurons of anterior raphe nuclei in the rat brain. Synapse1995; 19: 18–28. | Article | PubMed |
  43. Vilaro MT, Cortes R, Mengod G. Serotonin 5-HT4 receptors and their mRNAs in rat and guinea pig brain: distribution and effects of neurotoxic lesions. J Comp Neurol 2005; 484: 418–439. | Article | PubMed |
  44. Svenningsson P, Chergui K, Rachleff I, Flajolet M, Zhang X, El Yacoubi M et al. Alterations in 5-HT1B receptor function by p11 in depression-like states.Science 2006; 311: 77–80. | Article | PubMed | ISI | CAS |
  45. Warner-Schmidt JL, Flajolet M, Maller A, Chen EY, Qi H, Svenningsson P et al. Role of p11 in cellular and behavioral effects of 5-HT4 receptor stimulation. J Neurosci 2009; 29: 1937–1946. | Article | PubMed | ISI |
  46. Malleret G, Hen R, Guillou JL, Segu L, Buhot MC. 5-HT1B receptor knock-out mice exhibit increased exploratory activity and enhanced spatial memory performance in the Morris water maze. J Neurosci 1999; 19: 6157–6168. | PubMed | ISI | CAS |
  47. Segu L, Lecomte MJ, Wolff M, Santamaria J, Hen R, Dumuis A et al. Hyperfunction of muscarinic receptor maintains long-term memory in 5-HT4 receptor knock-out mice. PLoS ONE 2010; 5: e9529. | Article | PubMed |
  48. Francis HM, Kraushaar NJ, Hunt LR, Cornish JL. Serotonin 5-HT4 receptors in the nucleus accumbens are specifically involved in the appetite suppressant and not locomotor stimulant effects of MDMA ('ecstasy').Psychopharmacology (Berl) 2011; 213: 355–63. | Article | PubMed |
  49. Pratt WE, Blackstone K, Connolly ME, Skelly MJ. Selective serotonin receptor stimulation of the medial nucleus accumbens causes differential effects on food intake and locomotion. Behav Neurosci 2009; 123: 1046–1057. | Article | PubMed |
  50. Francis HM, Kraushaar NJ, Hunt LR, Cornish JL. Serotonin 5-HT4 receptors in the nucleus accumbens are specifically involved in the appetite suppressant and not locomotor stimulant effects of MDMA ('ecstasy').Psychopharmacology (Berl) 2010; 213: 355–363. | Article | PubMed |
  51. Bankson MG, Cunningham KA. 3,4-Methylenedioxymethamphetamine (MDMA) as a unique model of serotonin receptor function and serotonin-dopamine interactions. J Pharmacol Exp Ther 2001; 297: 846–852. | PubMed | ISI | CAS |
  52. Geyer MA. Serotonergic functions in arousal and motor activity. Behav Brain Res 1996; 73: 31–35. | Article | PubMed | CAS |
  53. Baumann MH, Clark RD, Rothman RB. Locomotor stimulation produced by 3,4-methylenedioxymethamphetamine (MDMA) is correlated with dialysate levels of serotonin and dopamine in rat brain. Pharmacol Biochem Behav2008; 90: 208–217. | Article | PubMed |
  54. Doly S, Valjent E, Setola V, Callebert J, Herve D, Launay JM et al. Serotonin 5-HT2B receptors are required for 3,4-methylenedioxymethamphetamine-induced hyperlocomotion and 5-HT release in vivo and in vitroJ Neurosci 2008; 28: 2933–2940. | Article | PubMed | ISI |
  55. Colado MI, O'Shea E, Green AR. Acute and long-term effects of MDMA on cerebral dopamine biochemistry and function. Psychopharmacology (Berl)2004; 173: 249–263. | Article | PubMed | CAS |
  56. Jaworski JN, Kozel MA, Philpot KB, Kuhar MJ. Intra-accumbal injection of CART (cocaine-amphetamine regulated transcript) peptide reduces cocaine-induced locomotor activity. J Pharmacol Exp Ther 2003; 307: 1038–1044. | Article | PubMed | CAS |
  57. Yang SC, Shieh KR, Li HY. Cocaine- and amphetamine-regulated transcript in the nucleus accumbens participates in the regulation of feeding behavior in rats. Neuroscience 2005; 133: 841–851. | Article | PubMed | CAS |
  58. Hubert GW, Kuhar MJ. Colocalization of CART with substance P but not enkephalin in the rat nucleus accumbens. Brain Res 2005; 1050: 8–14. | Article | PubMed | CAS |
  59. Hubert GW, Manvich DF, Kuhar MJ. Cocaine and amphetamine-regulated transcript-containing neurons in the nucleus accumbens project to the ventral pallidum in the rat and may inhibit cocaine-induced locomotion.Neuroscience 2009; 165: 179–187. | Article | PubMed |
  60. Maldonado-Irizarry CS, Swanson CJ, Kelley AE. Glutamate receptors in the nucleus accumbens shell control feeding behavior via the lateral hypothalamus. J Neurosci 1995; 15: 6779–6788. | PubMed | CAS |
  61. Stratford TR, Kelley AE. Evidence of a functional relationship between the nucleus accumbens shell and lateral hypothalamus subserving the control of feeding behavior. J Neurosci 1999; 19: 11040–11048. | PubMed | ISI | CAS |
  62. Stratford TR, Swanson CJ, Kelley A. Specific changes in food intake elicited by blockade or activation of glutamate receptors in the nucleus accumbens shell. Behav Brain Res 1998; 93: 43–50. | Article | PubMed | ISI | CAS |
  63. Verhagen LA, Luijendijk MC, de Groot JW, van Dommelen LP, Klimstra AG, Adan RA et al. Anticipation of meals during restricted feeding increases activity in the hypothalamus in rats. Eur J Neurosci 2011; 34: 1485–1491. | Article | PubMed |
  64. Heisler LK, Cowley MA, Tecott LH, Fan W, Low MJ, Smart JL et al. Activation of central melanocortin pathways by fenfluramine. Science 2002;297: 609–611. | Article | PubMed | ISI | CAS |
  65. Heisler LK, Jobst EE, Sutton GM, Zhou L, Borok E, Thornton-Jones Z et al. Serotonin reciprocally regulates melanocortin neurons to modulate food intake. Neuron 2006; 51: 239–249. | Article | PubMed | ISI | CAS |
  66. Aulakh CS, Hill JL, Wozniak KM, Murphy DL. Fenfluramine-induced suppression of food intake and locomotor activity is differentially altered by the selective type A monoamine oxidase inhibitor clorgyline.Psychopharmacology (Berl) 1988; 95: 313–317. | Article | PubMed |
  67. Heffner TG, Seiden LS. Possible involvement of serotonergic neurons in the reduction of locomotor hyperactivity caused by amphetamine in neonatal rats depleted of brain dopamine. Brain Res 1982; 244: 81–90. | Article | PubMed |
  68. Vickers SP, Benwell KR, Porter RH, Bickerdike MJ, Kennett GA, Dourish CT. Comparative effects of continuous infusion of mCPP, Ro 60-0175 and d-fenfluramine on food intake, water intake, body weight and locomotor activity in rats. Br J Pharmacol 2000; 130: 1305–1314. | Article | PubMed | ISI | CAS |
  69. Doly S, Bertran-Gonzalez J, Callebert J, Bruneau A, Banas SM, Belmer A et al. Role of serotonin via 5-HT2B receptors in the reinforcing effects of MDMA in mice. PLoS ONE 2009; 4: e7952. | Article | PubMed |
  70. Dumuis A, Bouhelal R, Sebben M, Cory R, Bockaert J. A nonclassical 5-hydroxytryptamine receptor positively coupled with adenylate cyclase in the central nervous system. Mol Pharmacol 1988; 34: 880–887. | PubMed | CAS |
  71. Self DW, Genova LM, Hope BT, Barnhart WJ, Spencer JJ, Nestler EJ. Involvement of cAMP-dependent protein kinase in the nucleus accumbens in cocaine self-administration and relapse of cocaine-seeking behavior. J Neurosci 1998; 18: 1848–1859. | PubMed | ISI | CAS |
  72. Rogge G, Jones D, Hubert GW, Lin Y, Kuhar MJ. CART peptides: regulators of body weight, reward and other functions. Nat Rev Neurosci 2008; 9: 747–758. | Article | PubMed | ISI |
Top

Acknowledgements

We greatly appreciate the help of E. Nestler, and the advices of R. Hen. We thank C. Dantec for the open-field data, L. Forichon and F. Arnal for mouse breeding and, M. Valbrun for her help in editing the text. Part of this study has been financially supported by ANR (Agence National de la Recherche: ANR-MNP 2009, SERFEED).

Supplementary Information accompanies the paper on the Translational Psychiatry website

Les commentaires sont fermés.