The CB1 receptor antagonist rimonabant reverses the diet-induced obesity phenotype through the regulation of lipolysis and energy balance.

We investigated the molecular events involved in the long-lasting reduction of adipose mass by the selective CB1 antagonist, SR141716. Its effects were assessed at the transcriptional level both in white (WAT) and brown (BAT) adipose tissues in a diet-induced obesity model in mice. Our data clearly indicated that SR141716 reversed the phenotype of obese adipocytes at both macroscopic and genomic levels. First, oral treatment with SR141716 at 10 mg/kg/d for 40 days induced a robust reduction of obesity, as shown by the 50% decrease in adipose mass together with a major restoration of white adipocyte morphology similar to lean animals. Second, we found that the major alterations in gene expression levels induced by obesity in WAT and BAT were mostly reversed in SR141716-treated obese mice. Importantly, the transcriptional patterns of treated obese mice were similar to those obtained in the CB1 receptor knockout mice fed a high-fat regimen and which are resistant to obesity, supporting a CB1 receptor-mediated process. Functional analysis of these modulations indicated that the reduction of adipose mass by the molecule resulted from an enhanced lipolysis through the induction of enzymes of the beta-oxidation and TCA cycle, increased energy expenditure, mainly through futile cycling (calcium and substrate), and a tight regulation of glucose homeostasis. These changes accompanied a significant cellular remodeling and contributed to a reduction of the obesity-related inflammatory status. In addition to a transient reduction of food consumption, increases of both fatty acid oxidation and energy expenditure induced by the molecule summate leading to a sustained weight loss. Altogether, these data strongly indicate that the endocannabinoid system has a major role in the regulation of energy metabolism.

Facilitation by endogenous tachykinins of the NMDA-evoked release of acetylcholine after acute and chronic suppression of dopaminergic transmission in the matrix of the rat striatum.

Using a microsuperfusion method in vitro, the effects of the NK1, NK2, and NK3 tachykinin receptor antagonists SR140333, SR48968, and SR142801, respectively, on the NMDA-evoked release of [3H]-acetylcholine were investigated after both acute and chronic suppression of dopamine transmission in striosomes and matrix of the rat striatum. NMDA (1 mm) alone or with D-serine (10 microm) in the presence of alpha-methyl-p-tyrosine (100 microm) markedly enhanced the release of [3H]-acetylcholine through a dopamine-independent inhibitory process. In both conditions, as well as after chronic 6-OHDA-induced denervation of striatal dopaminergic fibers, SR140333, SR48968, or SR142801 (0.1 microm each) reduced the NMDA-evoked release of [3H]-acetylcholine in the matrix but not in striosome-enriched areas. These responses were selectively abolished by coapplication with NMDA of the respective tachykinin agonists, septide, [Lys5,MeLeu9,Nle10]NKA(4-10), or senktide. Distinct mechanisms are involved in the effects of the tachykinin antagonists because the inhibitory response of SR140333 was additive with that of either SR48968 or SR142801. In addition, the SR140333-evoked response remained unchanged, whereas those of SR48968 and SR142801 were abolished in the presence of N(G)-monomethyl-l-arginine (nitric oxide synthase inhibitor). Therefore, in the matrix but not in striosomes, the acute or chronic suppression of dopamine transmission unmasked the facilitatory effects of endogenously released substance P, neurokinin A, and neurokinin B on the NMDA-evoked release of [3H]-acetylcholine. Whereas substance P and neurokinin A are colocalized in same efferent neurons, their responses involve distinct circuits because the substance P response seems to be mediated by NK1 receptors located on cholinergic interneurons, while those of neurokinin A and neurokinin B are nitric oxide-dependent.

Non-peptide vasopressin V1b receptor antagonists as potential drugs for the treatment of stress-related disorders.

Since vasopressin has been shown to be critical for adaptation of the hypothalamo-pituitary-adrenal axis during stress through its ability to potentiate the stimulatory effect of CRF, it has been hypothesized that this peptide may provide a good opportunity for pharmacological treatment of stress-related disorders. The availability of the first orally active non-peptide V(1b) receptor antagonist, SSR149415, opened a new era for examining the role of vasopressin in animal models of anxiety and depression. In rats, SSR149415 blocked several endocrine (i.e. ACTH release), neurochemical (i.e. noradrenaline release) and autonomic (i.e. hyperthermia) responses following various stress exposures. Moreover, the drug was able to attenuate some but not all stress-related behaviors in rodents. While the antidepressant-like activity of the compound was comparable to that of reference antidepressants, the overall profile displayed in anxiety tests was different from that of classical anxiolytics, such as benzodiazepines. These latter were highly effective and reliably produced robust effects in most anxiety tests, while SSR149415 showed clear-cut effects only in particularly stressful situations. Experiments with mice or hamsters indicated that V(1b) receptor blockade is associated with reduced aggressiveness, suggesting that SSR149415 could prove useful for treating aggressive behavior. It is important to note that SSR149415 is devoid of adverse effects on motor functions or cognitive processes, and it did not produce tolerance to its anxiolytic- or antidepressant-like activity. Altogether, these findings suggest that V(1b) receptor antagonists represent a promising alternative to agents currently used for the treatment of depression and some forms of anxiety disorders.

Nicotine-associated cues maintain nicotine-seeking behavior in rats several weeks after nicotine withdrawal: reversal by the cannabinoid (CB1) receptor antagonist, rimonabant (SR141716).

Conditioned stimuli are important for nicotine dependence and may trigger craving and relapse after prolonged nicotine abstinence. However, little is known about the pharmacology of this process. Among the systems that have been shown to play a role in drug-seeking behavior is the endocannabinoid transmission. Therefore, the present study examined the resistance to extinction of drug-seeking behavior elicited by nicotine-associated environmental stimuli and the effects of the selective CB1 cannabinoid antagonist rimonabant (SR141716) on the reinforcing effects of nicotine-related stimuli. Rats were trained to self-administer nicotine (0.03 mg/kg/injection, i.v.) under conditions in which responding was reinforced jointly by response-contingent nicotine injections and stimuli (light and tone). After self-administration acquisition, nicotine was withdrawn and lever pressing was only reinforced by contingent presentation of the audiovisual stimuli. Under such a condition, responding persisted for 3 months, following which nonpresentation of the cues produced a progressive extinction of responding. As expected, rats trained to lever-press for saline injections paired with the audiovisual stimuli did not acquire the self-administration. These findings indicate that the cues required learned association with nicotine to acquire reinforcing properties and to function as conditioned reinforcers. When administered 1 month following nicotine withdrawal, rimonabant (1 mg/kg, i.p.) decreased conditioned behavior. These results showing the persistence of a nicotine-conditioned behavior are congruent with the role of nicotine-related environmental stimuli in nicotine craving in abstinent smokers. Rimonabant, which has been shown previously to reduce nicotine self-administration, may be effective not only as an aid for smoking cessation but also in the maintenance of abstinence.

Neurochemical, electrophysiological and pharmacological profiles of the selective inhibitor of the glycine transporter-1 SSR504734, a potential new type of antipsychotic.

Noncompetitive N-methyl-D-aspartate (NMDA) blockers induce schizophrenic-like symptoms in humans, presumably by impairing glutamatergic transmission. Therefore, a compound potentiating this neurotransmission, by increasing extracellular levels of glycine (a requisite co-agonist of glutamate), could possess antipsychotic activity. Blocking the glycine transporter-1 (GlyT1) should, by increasing extracellular glycine levels, potentiate glutamatergic neurotransmission. SSR504734, a selective and reversible inhibitor of human, rat, and mouse GlyT1 (IC50=18, 15, and 38 nM, respectively), blocked reversibly the ex vivo uptake of glycine (mouse cortical homogenates: ID50: 5 mg/kg i.p.), rapidly and for a long duration. In vivo, it increased (minimal efficacious dose (MED): 3 mg/kg i.p.) extracellular levels of glycine in the rat prefrontal cortex (PFC). This resulted in an enhanced glutamatergic neurotransmission, as SSR504734 potentiated NMDA-mediated excitatory postsynaptic currents (EPSCs) in rat hippocampal slices (minimal efficacious concentration (MEC): 0.5 microM) and intrastriatal glycine-induced rotations in mice (MED: 1 mg/kg i.p.). It normalized activity in rat models of hippocampal and PFC hypofunctioning (through activation of presynaptic CB1 receptors): it reversed the decrease in electrically evoked [3H]acetylcholine release in hippocampal slices (MEC: 10 nM) and the reduction of PFC neurons firing (MED: 0.3 mg/kg i.v.). SSR504734 prevented ketamine-induced metabolic activation in mice limbic areas and reversed MK-801-induced hyperactivity and increase in EEG spectral energy in mice and rats, respectively (MED: 10-30 mg/kg i.p.). In schizophrenia models, it normalized a spontaneous prepulse inhibition deficit in DBA/2 mice (MED: 15 mg/kg i.p.), and reversed hypersensitivity to locomotor effects of d-amphetamine and selective attention deficits (MED: 1-3 mg/kg i.p.) in adult rats treated neonatally with phencyclidine. Finally, it increased extracellular dopamine in rat PFC (MED: 10 mg/kg i.p.). The compound showed additional activity in depression/anxiety models, such as the chronic mild stress in mice (10 mg/kg i.p.), ultrasonic distress calls in rat pups separated from their mother (MED: 1 mg/kg s.c.), and the increased latency of paradoxical sleep in rats (MED: 30 mg/kg i.p.). In conclusion, SSR504734 is a potent and selective GlyT1 inhibitor, exhibiting activity in schizophrenia, anxiety and depression models. By targeting one of the primary causes of schizophrenia (hypoglutamatergy), it is expected to be efficacious not only against positive but also negative symptoms, cognitive deficits, and comorbid depression/anxiety states.

Blockade by the cannabinoid CB1 receptor antagonist, rimonabant (SR141716), of the potentiation by quinelorane of food-primed reinstatement of food-seeking behavior.

It has been shown previously that the selective cannabinoid CB1 receptor antagonist, rimonabant (SR141716), reduced the intake of palatable food as well as the self-administration of several drugs of abuse, suggesting that endocannabinoid systems play a role in brain reward function. The present study investigated whether a cannabinoid step was involved in food-seeking behavior induced by explicit stimuli, using an operant reinstatement procedure in rats. Experimental sessions consisted of a 15-min food rewarded period, followed by a 45-min extinction period. Rimonabant did not affect the response reinstatement induced by noncontingent delivery of food pellets, but prevented (0.03-0.3 mg/kg) the potentiation by quinelorane, a dopamine D3 receptor-preferring agonist, of food-seeking behavior. A possible link between cannabinoid processes and D3- and/or D2-mediated dopaminergic transmission was further investigated by studying Fos protein expression in cortico-limbic structures in D3 (D3-/-) and D2 (D2-/-) knockout mice. Rimonabant (10 mg/kg) increased Fos immunoreactivity in the prefrontal cortex (pFCortex) and in the shell but not the core of the nucleus accumbens (NAcc). Fos induction by this dose of rimonabant was not seen in mice lacking CB1 receptors, providing clear evidence for the involvement of CB1 receptors. In the NAcc shell, the effect of rimonabant was suppressed in D3-/-, but remained unchanged in D2-/- mice. In contrast, Fos expression by rimonabant in the pFCortex was impervious to D2 or D3 receptor deletion. In conclusion, these data indicate first that rimonabant prevented the enhancement by quinelorane of the appetitive value of food pellets unexpectedly delivered during extinction and second that rimonabant effects might involve D3 receptor-mediated processes. Overall, these results are consistent with the notion that endocannabinoid functions control brain reward processes and in particular the capacity of explicit stimuli to precipitate food-seeking behavior.

SSR181507, a dopamine D2 receptor antagonist and 5-HT1A receptor agonist. II: Behavioral profile predictive of an atypical antipsychotic activity.

SSR181507 ((3-exo)-8-benzoyl-N-(((2S)7-chloro-2,3-dihydro-1,4-benzodioxin-1-yl)methyl)-8-azabicyclo(3.2.1)octane-3-methanamine monohydrochloride) is a novel tropanemethanamine benzodioxane that displays antagonist activity at dopamine D(2) receptors and agonist activity at 5-HT(1A) receptors. SSR181507 antagonized apomorphine-induced climbing in mice and stereotypies in rats (ED(50) of 2 and 3.4 mg/kg i.p., respectively) and blocked D-amphetamine-induced hyperlocomotion in rats at lower doses (0.3-1 mg/kg i.p.). At 1-10 mg/kg, it was found to disrupt active avoidance in mice. SSR181507 did not induce catalepsy in rats (MED>60 mg/kg i.p.) and antagonized (3-10 mg/kg i.p.) haloperidol-induced catalepsy. SSR181507 was also active in two models sensitive to antidepressant/anxiolytic drugs: in a guinea-pig pup/mother separation test, it decreased (1-3 mg/kg i.p.) the time spent vocalizing during the separation episode, and in a lithium-induced taste aversion procedure in rats, it partially reversed (3 mg/kg i.p.) the decrease of intake of a saccharin solution. Furthermore, SSR181507 increased (3 mg/kg i.p.) the latency time to paradoxical sleep in rats, an effect commonly observed with antidepressants. Coadministration of the selective 5-HT(1A) blocker SL88.0338 produced catalepsy and antagonized the effects of SSR181507 in the depression/anxiety tests, confirming the view that activation of 5-HT(1A) receptors confers an atypical profile on SSR181507, and is responsible for its antidepressant/anxiolytic properties. Finally, SSR181507 (1-3 mg/kg) did not affect memory performance in a Morris water maze task in rats. The pharmacological profile of SSR181507 suggests that it should control the symptoms of schizophrenia, in the absence of extrapyramidal signs and cognitive deficits, with the additional benefit of antidepressant/anxiolytic activities.

SSR181507, a dopamine D(2) receptor antagonist and 5-HT(1A) receptor agonist. I: Neurochemical and electrophysiological profile.

SSR181507 ((3-exo)-8-benzoyl-N-[[(2S)7-chloro-2,3-dihydro-1,4-benzodioxin-1-yl]methyl]-8-azabicyclo[3.2.1]octane-3-methanamine monohydrochloride) is a novel tropanemethanamine benzodioxane derivative that possesses high and selective affinities for D2-like and 5-HT(1A) receptors (K(I)=0.8, 0.2, and 0.2 nM for human D(2), D(3), and 5-HT(1A), respectively). In vivo, SSR181507 inhibited [(3)H]raclopride binding to D(2) receptors in the rat (ID(50)=0.9 and 1 mg/kg, i.p. in limbic system and striatum, respectively). It displayed D(2) antagonist and 5-HT(1A) agonist properties in the same concentration range in vitro (IC(50)=5.3 nM and EC(50)=2.3 nM, respectively, in the GTPgammaS model) and in the same dose range in vivo (ED(50)=1.6 and 0.7 mg/kg, i.p. on striatal DA and 5-HT synthesis, respectively, and 0.03-0.3 mg/kg, i.v. on dorsal raphe nucleus firing rate). It selectively enhanced Fos immunoreactivity in mesocorticolimbic areas as compared to the striatum. This regional selectivity was confirmed in electrophysiological studies where SSR181507, given acutely (0.1-3 mg/kg, i.p.) or chronically (3 mg/kg, i.p., o.d., 22 days), increased or decreased, respectively, the number of spontaneous active DA cells in the ventral tegmental area, but not in the substantia nigra. Moreover, SSR181507 increased both basal and phasic DA efflux (as assessed by microdialysis and electrochemistry) in the medial prefrontal cortex and nucleus accumbens, but not in the striatum. This study shows that the combination of D(2) receptor antagonism and 5-HT(1A) agonism, in the same dose range, confers on SSR181507 a unique neurochemical and electrophysiological profile and suggests the potential of this compound for the treatment of the main dimensions of schizophrenia.

Targeted inactivation of the neurotensin type 1 receptor reveals its role in body temperature control and feeding behavior but not in analgesia.

Three subtypes of neurotensin receptor have been described, two members of the heptahelical transmembrane domain G protein-coupled receptor superfamily NT-1R and NT-2R, and NT-3R unrelated to this family. We have generated NT-1R deficient (NT-1R(-/-)) mice. NT-1R(-/-) mice were born at the expected Mendelian frequency without obvious abnormalities and they were fertile. The NT-induced analgesia on the writhing induced by phenyl-p-benzoquinone administration remained at wild-type levels in the NT-1R(-/-) mice demonstrating that the NT-1R is not implicated in the analgesic effect of NT in this test. The NT-1R(-/-) mice were hyperthermic; their body temperature was not affected by intracerebroventricular (i.c.v.) administration of NT, contrasting with the hypothermia induced in NT-1R(+/+) mice. NT-1R(-/-) mice showed a small significant increase in body weight compared to the NT-1R(+/+) congeners as early as 10 weeks after birth, correlated with a higher food intake. NT-1R(-/-) mice showed similar spontaneous locomotion to the control littermates, but did not respond to i.c.v. NT-induced hypolocomotion. I.c.v. injection of NT inhibited feeding in fasted wild-type mice, but had no effect on feeding of the NT-1R(-/-) mice. I.c.v. administration of the orexigenic neuropeptide Y (NPY) stimulated feeding to the same extent in both wild-type and NT-1R(-/-) mice. This analysis of NT-1R-deficient mice shows that the NT-1R does not play a role in NT-induced analgesia, but that it is clearly implicated in thermal and feeding regulation, weight control, and NT-induced hypolocomotion.

Overeating, alcohol and sucrose consumption decrease in CB1 receptor deleted mice.

Administration of the cannabinoid CB1 receptor antagonist SR141716 (3-10 mg/kg i.p.) abolished neuropeptide Y-induced overeating and significantly reduced ethanol and sucrose intake in CB1 wild-type (+/+) mice. In CB1 receptor knockout (-/-) mice, neuropeptide Y totally lost its capacity to increase food consumption. Similarly, sucrose and ethanol intakes were significantly lower in CB1-/- vs. CB1+/+ mice. In CB1 deficient mice, SR141716 had no effect in these models.

The neurotensin receptor antagonist SR 142948A blocks the efflux of dopamine evoked in nucleus accumbens by neurotensin ejection into the ventral tegmental area.

The neuropeptide neurotensin (NT) exerts a wide range of central and peripheral effects. In particular, ejection of NT (10(-7) M, 65 nl) into the ventral tegmental area (VTA) in anaesthetised rats pre-treated with pargyline increases the dopamine (DA) efflux within the nucleus accumbens (NAcc) as measured by differential pulse amperometry (DPA) combined with carbon fibre electrodes. However, this effect is not blocked by systemic pre-treatment with the potent and selective non-peptide NT receptor antagonists SR 48692 and SR 142948A, at any dose studied. The present study was designed to determine the ability of these NT receptor antagonists to block the increase in DA efflux evoked within the NAcc when they are locally applied with the peptide into the VTA. The competitive N-methyl- D-aspartate (NMDA) receptor antagonist, 2-amino-5-phosphonopentanoic acid (AP-5), applied into the VTA 1 min before NMDA, blocked the effect of NMDA on DA efflux concentration and volume dependently, thus demonstrating the suitability of our experimental procedure for characterizing both an agonist and an antagonist specific for receptors present on mesencephalic dopaminergic neurons and involved in the regulation of DA efflux within the NAcc. Intra-VTA application of SR 142948A blocked the NT-evoked increase in DA efflux within the NAcc dose dependently whereas SR 48692, at the concentration used, was inactive. These results suggest that NT regulates mesencephalic dopaminergic activity through NT receptors sensitive to SR 142948A, but possibly not to SR 48692.

Rimonabant reduces obesity-associated hepatic steatosis and features of metabolic syndrome in obese Zucker fa/fa rats.

This study investigated the effects of rimonabant (SR141716), an antagonist of the cannabinoid receptor type 1 (CB1), on obesity-associated hepatic steatosis and related features of metabolic syndrome: inflammation (elevated plasma levels of tumor necrosis factor alpha [TNFalpha]), dyslipidemia, and reduced plasma levels of adiponectin. We report that oral treatment of obese (fa/fa) rats with rimonabant (30 mg/kg) daily for 8 weeks abolished hepatic steatosis. This treatment reduced hepatomegaly, reduced elevation of plasma levels of enzyme markers of hepatic damage (alanine aminotransferase, gamma glutamyltransferase, and alkaline phosphatase) and decreased the high level of local hepatic TNFalpha currently associated with steatohepatitis. In parallel, treatment of obese (fa/fa) rats with rimonabant reduced the high plasma level of the proinflammatory cytokine TNFalpha and increased the reduced plasma level of the anti-inflammatory hormone adiponectin. Finally, rimonabant treatment also improved dyslipidemia by both decreasing plasma levels of triglycerides, free fatty acids, and total cholesterol and increasing the HDLc/LDLc ratio. All the effects of rimonabant found in this study were not or only slightly observed in pair-fed obese animals, highlighting the additional beneficial effects of treatment with rimonabant compared to diet. These results demonstrate that rimonabant plays a hepatoprotective role and suggest that this CB1 receptor antagonist potentially has clinical applications in the treatment of obesity-associated liver diseases and related features of metabolic syndrome.

Effects of CB1 cannabinoid receptor blockade on ethanol preference after chronic alcohol administration combined with repeated re-exposures and withdrawals.

AIMS: The cannabinoid CB1 receptor antagonist, SR141716A, differentially affects the ethanol preference of chronically alcoholized rats when administered during cycles of ethanol exposure and withdrawal. In this study, ethanol preference was investigated in chronically alcoholized rats that underwent regular withdrawal periods during which the brain cannabinoid CB(1) receptor antagonist, SR141716A, was administered. METHODS: The cannabinoid receptor antagonist SR141716A, 3 or 10 mg/kg/day, was administered i.p. to Wistar rats at the conclusion of a 4-week period of chronic alcoholization, as they commenced a cycle of alcohol withdrawal for 10 days followed by a period of 10 days chronic ethanol exposure. In a second set of experiments, an additional cycle of ethanol withdrawal and re-exposure was given. Preference for ethanol versus water started at the end of the first or second chronic ethanol re-exposure for a period of at least 30 days. RESULTS: In rats pretreated with the higher dose of SR141716A, ethanol preference during free choice was significantly increased after two ethanol re-exposures. In contrast, pretreatment with the lower SR141716A dose induced no significant change in ethanol intake during the free choice followed by either one or two ethanol re-exposures. CONCLUSIONS: SR141716A, 10 mg/kg/day dose, induced a significant increase in ethanol preference which was dependent on both the number of ethanol withdrawals and chronic ethanol re-exposures, while 3 mg/kg/day had no significant effect on ethanol preference.

The new neurokinin 1-sensitive receptor mediates the facilitation by endogenous tachykinins of the NMDA-evoked release of acetylcholine after suppression of dopaminergic transmission in the matrix of the rat striatum.

Using an in vitro microsuperfusion procedure, the NMDA-evoked release of [3H]ACh was studied after suppression of dopamine (DA) transmission (alpha-methyl-p-tyrosine) in striatal compartments of the rat. The effects of tachykinin neurokinin 1 (NK1) receptor antagonists and the ability of appropriate agonists to counteract the antagonist responses were investigated to determine whether tachykinin NK1 classic, septide-sensitive and/or new NK1-sensitive receptors mediate these regulations. The NK1 antagonists, SR140333, SSR240600, GR205171 but not GR82334 and RP67580 (0.1 and 1 microM) markedly reduced the NMDA (1 mm + D-serine 10 microM)-evoked release of [3H]ACh only in the matrix. These responses unchanged by coapplication with NMDA of NK2 or NK3 agonists, [Lys5,MeLeu9,Nle10]NKA(4-10) or senktide, respectively, were completely counteracted by the selective NK1 agonist, [Pro9]substance P but also by neurokinin A and neuropeptide K (1 nM each). According to the rank order of potency of agonists for counteracting the antagonist responses ([Pro9]substance P, 0.013 nM > neurokinin A, 0.15 nM >> substance P(6-11) 7.7 nM = septide 8.7 nM), the new NK1-sensitive receptors mediate the facilitation by endogenous tachykinins of the NMDA-evoked release of ACh in the matrix, after suppression of DA transmission. Solely the NK1 antagonists having a high affinity for these receptors could be used as indirect anti-cholinergic agents.

Expression profile and up-regulation of PRAX-1 mRNA by antidepressant treatment in the rat brain.

A protein associated with the peripheral-type benzodiazepine receptor (PRAX-1) has recently been cloned, but its regional distribution in the central nervous system and its function remain to be clarified. In situ hybridization was carried out to localize PRAX-1 mRNA in the rat brain and revealed a high expression of the transcript in limbic structures such as the CA1 region of the hippocampus, as well as the dentate gyrus, septum, amygdala, and the islands of Calleja. A dense hybridization signal was also observed in the nucleus accumbens, caudate nucleus, olfactory tubercle, pineal gland, and cerebellar cortex. PRAX-1 mRNA expression was largely neuronal; it colocalized with neuron-specific enolase but not glial fibrillary acidic protein. Long-term treatments (21 days) with the neuroleptic haloperidol increased PRAX-1 mRNA expression only in the dentate gyrus, whereas anxiolytic/anticonvulsant diazepam had no effect in any of the hippocampal region studied. Repeated electroconvulsive shock administration significantly enhanced PRAX1 expression in the CA1 subfield and dentate gyrus. Several classes of antidepressant treatment, including serotonin selective reuptake inhibitor (fluoxetine), mixed serotonin- and norepinephrine-uptake inhibitor (imipramine), and monoamine oxidase inhibitors (iproniazid and tranylcypromine), shared this effect. Furthermore, the selective nonpeptide NK2 receptor antagonist (S)-N-methyl-N-[4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl)butyl]benzamide (SR48968), which shows an antidepressant profile in animal studies, also enhanced PRAX-1 mRNA expression. These results point to a potential role of PRAX-1 function in the central nervous system and suggest that the up-regulation of PRAX-1 mRNA represents a common action of chronic antidepressant treatment.

Anti-obesity effect of SR141716, a CB1 receptor antagonist, in diet-induced obese mice.

Because the CB1 receptor antagonist SR141716 was previously reported to modulate food intake in rodents, we studied its efficacy in reducing obesity in a diet-induced obesity (DIO) model widely used for research on the human obesity syndrome. During a 5-wk treatment, SR141716 (10 mg. kg(-1). day(-1) orally) induced a transient reduction of food intake (-48% on week 1) and a marked but sustained reduction of body weight (-20%) and adiposity (-50%) of DIO mice. Furthermore, SR141716 corrected the insulin resistance and lowered plasma leptin, insulin, and free fatty acid levels. Most of these effects were present, but less pronounced at 3 mg. kg(-1). day(-1). In addition to its hypophagic action, SR141716 may influence metabolic processes as the body weight loss of SR141716-treated mice was significantly higher during 24-h fasting compared with vehicle-treated animals, and when a 3-day treatment was compared with a pair feeding. SR141716 had no effect in CB1 receptor knockout mice, which confirmed the implication of CB1 receptors in the activity of the compound. These findings suggest that SR141716 has a potential as a novel anti-obesity treatment.

Direct and indirect interactions between cannabinoid CB1 receptor and group II metabotropic glutamate receptor signalling in layer V pyramidal neurons from the rat prefrontal cortex.

At proximal synapses from layer V pyramidal neurons from the rat prefrontal cortex, activation of group II metabotropic glutamate receptors (group II mGlu) by (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl) glycine (DCG IV) induced a long-lasting depression of excitatory postsynaptic currents. Paired-pulse experiments suggested that the depression was expressed presynaptically. Activation of type 1 cannabinoid receptors (CB1) by WIN 55,212-2 occluded the DCG IV-induced depression in a mutually occlusive manner. At the postsynaptic level, WIN 55,212-2 and DCG IV were also occlusive for the activation of extracellular signal-regulated kinase. The postsynaptic localization of active extracellular signal-regulated kinase was confirmed by immunocytochemistry after activation of CB1 receptors. However, phosphorylation of extracellular signal-regulated kinase in layer V pyramidal neurons was dependent on the activation of N-methyl-d-aspartate receptors, consequently to a release of glutamate in the local network. Group II mGlu were also shown to be involved in long-term changes in synaptic plasticity induced by high frequency stimulations. The group II mGlu antagonist (RS)-alpha-methylserine-O-phosphate monophenyl ester (MSOPPE) favoured long-term depression. However, no interaction was found between MSOPPE, WIN 55,212-2 and the CB1 receptor antagonist SR 141716A on the modulation of long-term depression or long-term potentiation and the effects of these drugs were rather additive. We suggest that CB1 receptor and group II mGlu signalling may interact through a presynaptic mechanism in the induction of a DCG IV-induced depression. Postsynaptically, an indirect interaction occurs for activation of extracellular signal-regulated kinase. However, none of these interactions seem to play a role in synaptic plasticities induced with high frequency stimulations.

Specific involvement of neurotensin type 1 receptor in the neurotensin-mediated in vivo dopamine efflux using knock-out mice.

Abstract Neurotensin is a tridecapeptide neurotransmitter known to be involved in psychiatric disorders, various physiological processes and several different neurobiological mechanisms, including modulation of accumbal dopamine release. Two neurotensin extracellular binding sites, namely NT1- and NT2-receptor (NT1R and NT2R), have been cloned from the rat brain. These receptors are distinguishable by their different in vitro pharmacological properties but the available pharmacological tools have weak in vivo potency and specificity. The use of genetically engineered knock-out mice has provided a powerful alternative to the classical pharmacological approach to investigate their respective roles. In this study, using in vivo differential pulse amperometry, we show that, in wild-type mice, neurotensin application into the ventral tegmental area dose-dependently evokes dopamine efflux in the nucleus accumbens. This neurotensin-mediated efflux is dramatically decreased in mice lacking NT1R while it is unaffected in NT2R-deleted mice. This finding indicates that a large part of the dopamine efflux evoked by neurotensin in the nucleus accumbens of wild-type mice is mediated via NT1R present in the ventral tegmental area.

Permissive role of neurokinin NK(3) receptors in NK(1) receptor-mediated activation of the locus coeruleus revealed by SR 142801.

The present experiments investigated the role of neurokinin-1 (NK(1)) and neurokinin-3 (NK(3)) receptors on the activity of the locus coeruleus (LC)-noradrenergic system by using a dual probe microdialysis technique in anesthetized guinea pigs. The local application in the LC of the selective NK(1) receptor agonists [SAR(9),Met(O(2))(11)]-SP (10 microM) and septide (1 microM) as well as the selective NK(3) receptor agonist senktide (1 microM), enhanced the extracellular norepinephrine (NE) levels in the prefrontal cortex. The enhancing effect of [SAR(9),Met(O(2))(11)]-SP was completely blocked by the peripheral administration of the selective non peptide NK(1) and NK(3) receptor antagonists, GR 205171 (1 mg/kg, i.p.) and SR 142801 (0.1 mg/kg, i.p.), respectively, whereas SR 142806 (0.1 mg/kg, i.p.) the inactive enantiomer of SR 142801 had no effect. Moreover, the [SAR(9),Met(O(2))(11)]-SP-induced increase in LC DOPAC concentrations, is only antagonized by GR 205171. In contrast, only SR 142801 (0.3 mg/kg, i.p.) could block stereoselectively the senktide-evoked increase in NE levels. Both [SAR(9),Met(O(2))(11)]-SP and senktide effects were blocked by local infusion into the LC of SR 142801 (10(-9) M). These results demonstrate that stimulation of NK(1) and NK(3) receptors located in the LC area modulates the activity of the LC-NE system, and that the excitatory effects of NK(1) receptor agonists require NKB/NK(3) receptor activation in the LC.

4-(2-Chloro-4-methoxy-5-methylphenyl)-N-[(1S)-2-cyclopropyl-1-(3-fluoro-4-methylphenyl)ethyl]5-methyl-N-(2-propynyl)-1, 3-thiazol-2-amine hydrochloride (SSR125543A), a potent and selective corticotrophin-releasing factor(1) receptor antagonist. II. Characterization in rodent models of stress-related disorders.

The present study investigated the effects of the novel corticotrophin-releasing factor (CRF)(1) receptor antagonist 4-(2-chloro-4-methoxy-5-methylphenyl)-N-[(1S)-2-cyclopropyl-1-(3-fluoro-4-methylphenyl)ethyl]5-methyl-N-(2-propynyl)-1,3-thiazol-2-amine hydrochloride (SSR125543A) in a variety of rodent models of anxiety, including conflict procedures (punished drinking and four-plate), exploration models (elevated plus-maze and light/dark), a fear/anxiety defense test battery, and several procedures based on stress-induced changes in physiological (isolation-induced hyperthermia and tail pinch-induced cortical norepinephrine release) or behavioral (social defeat-induced anxiety, maternal separation-induced vocalization) parameters. Moreover, the effects of SSR125543A were investigated in acute (forced swimming) and chronic (chronic mild stress; CMS) models of depression. SSR125543A and the CRF(1) receptor antagonist antalarmin displayed limited efficacy in exploration-based anxiety models. In contrast, both compounds produced clear-cut anxiolytic-like activity in models involving inescapable stress, including the conflict procedures, the social defeat-induced anxiety paradigm and the defense test battery (3-30 mg/kg i.p. or p.o.). These effects paralleled those of the anxiolytic diazepam. In addition, SSR125543A and antalarmin antagonized stress-induced hyperthermia, distress vocalization, and cortical norepinephrine release. In the forced swimming test, 30 mg/kg p.o. SSR125543A and 3 to 30 mg/kg p.o. antalarmin produced clear antidepressant-like effects. These latter results were strengthened by the findings from the CMS, which showed that repeated administration of 10 mg/kg i.p. SSR125543A for 30 days improved the degradation of the physical state, the reduction of body weight gain, and anxiety produced by stress. Together, these data indicate that SSR125543A shows good activity in acute and chronic tests of unavoidable stress exposure, suggesting that it may have a potential in the treatment of depression and some forms of anxiety disorders.