Synthesis and preliminary evaluation of a new fluorine-18 labelled triazine derivative for PET imaging of cannabinoid CB2 receptor.

Cannabinoid CB2 PET tracers are considered as a promising alternative to PBR/TSPO tracers for the in-vivo imaging of neuroinflammation. We describe here the synthesis and characterization of compound 3, a new potent and brain penetrating CB2 ligand based on an original triazine template. The PET tracer [(18)F]-dideutero-3 was prepared in a three steps radiosynthesis, and demonstrated significant uptake in rhesus macaque and baboon brain with a maximum SUV of about 0.7-0.9g/mL, followed by a moderate washout over time.

Characterization of SSR103800, a selective inhibitor of the glycine transporter-1 in models predictive of therapeutic activity in schizophrenia.

On native human, rat and mouse glycine transporter-1(GlyT1), SSR130800 behaves as a selective inhibitor with IC50 values of 1.9, 5.3 and 6.8 nM, respectively. It reversibly blocked glycine uptake in mouse brain cortical homogenates, increased extracellular levels of glycine in the rat prefrontal cortex, and potentiated NMDA-mediated excitatory postsynaptic currents in rat hippocampal slices. SSR103800 (30 mg/kg, p.o.) decreased MK-801- and PCP-induced locomotor hyperactivity in rodents. SSR103800 (1 and 10 mg/kg, p.o.) attenuated social recognition deficit in adult rats induced by neonatal injections of PCP (10 mg/kg, s.c., on post-natal day 7, 9 and 11). SSR103800 (3 mg/kg, p.o.) counteracted the deficit in short-term visual episodic-like memory induced by a low challenge dose of PCP (1 mg/kg, i.p.), in PCP-sensitized rats (10 mg/kg, i.p.). SSR103800 (30 mg/kg, i.p.) increased the prepulse inhibition of the startle reflex in DBA/1J mice. SSR103800 decreased defensive- and despair-related behaviors in the tonic immobility test in gerbils (10 and 30 mg/kg, p.o.) and in the forced-swimming procedure in rats (1 and 3 mg/kg, p.o.), respectively. These findings suggest that SSR103800 may have a therapeutic potential in the management of the core symptoms of schizophrenia and comorbid depression states.

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.

SSR180711, a novel selective alpha7 nicotinic receptor partial agonist: (1) binding and functional profile.

In this paper, we report on the pharmacological and functional profile of SSR180711 (1,4-Diazabicyclo[3.2.2]nonane-4-carboxylic acid, 4-bromophenyl ester), a new selective alpha7 acetylcholine nicotinic receptor (n-AChRs) partial agonist. SSR180711 displays high affinity for rat and human alpha7 n-AChRs (K(i) of 22+/-4 and 14+/-1 nM, respectively). Ex vivo (3)[H]alpha-bungarotoxin binding experiments demonstrate that SSR180711 rapidly penetrates into the brain (ID(50)=8 mg/kg p.o.). In functional studies performed with human alpha7 n-AChRs expressed in Xenopus oocytes or GH4C1 cells, the compound shows partial agonist effects (intrinsic activity=51 and 36%, EC(50)=4.4 and 0.9 microM, respectively). In rat cultured hippocampal neurons, SSR180711 induced large GABA-mediated inhibitory postsynaptic currents and small alpha-bungarotoxin sensitive currents through the activation of presynaptic and somato-dendritic alpha7 n-AChRs, respectively. In mouse hippocampal slices, the compound increased the amplitude of both glutamatergic (EPSCs) and GABAergic (IPSCs) postsynaptic currents evoked in CA1 pyramidal cells. In rat and mouse hippocampal slices, a concentration of 0.3 muM of SSR180711 increased long-term potentiation (LTP) in the CA1 field. Null mutation of the alpha7 n-AChR gene totally abolished SSR180711-induced modulation of EPSCs, IPSCs and LTP in mice. Intravenous administration of SSR180711 strongly increased the firing rate of single ventral pallidum neurons, extracellularly recorded in anesthetized rats. In microdialysis experiments, administration of the compound (3-10 mg/kg i.p.) dose-dependently increased extracellular acetylcholine (ACh) levels in the hippocampus and prefrontal cortex of freely moving rats. Together, these results demonstrate that SSR180711 is a selective and partial agonist at human, rat and mouse alpha7 n-AChRs, increasing glutamatergic neurotransmission, ACh release and LTP in the hippocampus.

SSR180711, a novel selective alpha7 nicotinic receptor partial agonist: (II) efficacy in experimental models predictive of activity against cognitive symptoms of schizophrenia.

SSR180711 (4-bromophenyl 1,4diazabicyclo(3.2.2) nonane-4-carboxylate, monohydrochloride) is a selective alpha7 nicotinic receptor (n-AChR) partial agonist. Based on the purported implication of this receptor in cognitive deficits associated with schizophrenia, the present study assessed efficacy of SSR180711 (i.p. and p.o.) in different types of learning and memory involved in this pathology. SSR180711 enhanced episodic memory in the object recognition task in rats and mice (MED: 0.3 mg/kg), an effect mediated by the alpha7 n-AChR, as it was no longer seen in mice lacking this receptor. Efficacy was retained after repeated treatment (eight administrations over 5 days, 1 mg/kg), indicating lack of tachyphylaxia. SSR180711 also reversed (MED: 0.3 mg/kg) MK-801-induced deficits in retention of episodic memory in rats (object recognition). The drug reversed (MED: 0.3 mg/kg) selective attention impaired by neonatal phencyclidine (PCP) treatment and restored MK-801- or PCP-induced memory deficits in the Morris or linear maze (MED: 1-3 mg/kg). In neurochemical and electrophysiological correlates of antipsychotic drug action, SSR180711 increased extracellular levels of dopamine in the prefrontal cortex (MED: 1 mg/kg) and enhanced (3 mg/kg) spontaneous firing of retrosplenial cortex neurons in rats. Selectivity of SSR180711 was confirmed as these effects were abolished by methyllycaconitine (3 mg/kg, i.p. and 1 mg/kg, i.v., respectively), a selective alpha7 n-AChR antagonist. Additional antidepressant-like properties of SSR180711 were demonstrated in the forced-swimming test in rats (MED: 1 mg/kg), the maternal separation-induced ultrasonic vocalization paradigm in rat pups (MED: 3 mg/kg) and the chronic mild stress procedure in mice (10 mg/kg o.d. for 3 weeks). Taken together, these findings characterize SSR180711 as a promising new agent for the treatment of cognitive symptoms of schizophrenia. The antidepressant-like properties of SSR180711 are of added interest, considering the high prevalence of depressive symptoms in schizophrenic patients.

The cannabinoid CB1 receptor antagonist rimonabant (SR141716) inhibits cell proliferation and increases markers of adipocyte maturation in cultured mouse 3T3 F442A preadipocytes.

Adipocyte cell proliferation is an important process in body fat mass development in obesity. Adiponectin or Acrp30 is an adipocytokine exclusively expressed and secreted by adipose tissue that regulates lipid and glucose metabolism and plays a key role in body weight regulation and homeostasis. Adiponectin mRNA expression in adipose tissue and plasma level of adiponectin are decreased in obesity and type 2 diabetes. In obese rodents, the selective CB(1) receptor antagonist rimonabant reduces food intake and body weight and improves lipid and glucose parameters. We have reported previously that rimonabant stimulated adiponectin mRNA expression in adipose tissue of obese fa/fa rats, by a direct effect on adipocytes. We report here that rimonabant (10-400 nM) inhibits cell proliferation of cultured mouse 3T3 F442A preadipocytes in a concentration-dependent manner. In parallel to this inhibitory effect on preadipocyte cell proliferation, rimonabant (25-100 nM) stimulates mRNA expression and protein levels of two late markers of adipocyte differentiation (adiponectin and glyceraldehyde-3-phosphate dehydrogenase) with a maximal effect at 100 nM, without inducing the accumulation of lipid droplets. Furthermore, treatment of mouse 3T3 F442A preadipocytes with rimonabant (100 nM) inhibits basal and serum-induced p42/44 mitogen-activated protein (MAP) kinase activity. These results suggest that inhibition of MAP kinase activity by rimonabant may be one of mechanisms involved in the inhibition of 3T3 F442A preadipocyte cell proliferation and stimulation of adiponectin and GAPDH expression. The inhibition of preadipocyte cell proliferation and the induction of adipocyte late "maturation" may participate in rimonabant-induced antiobesity effects, particularly the reduction of body fat mass.

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.

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.

SSR240600 [(R)-2-(1-[2-[4-[2-[3,5-bis(trifluoromethyl)phenyl]acetyl]-2-(3,4-dichlorophenyl)-2-morpholinyl]ethyl]- 4-piperidinyl)-2-methylpropanamide], a centrally active nonpeptide antagonist of the tachykinin neurokinin-1 receptor: I. biochemical and pharmacological characterization.

The biochemical and pharmacological properties of a novel antagonist of the tachykinin neurokinin 1 (NK1) receptor, SSR240600 [(R)-2-(1-[2-[4-[2-[3,5-bis(trifluoromethyl)phenyl]acetyl]-2-(3,4-dichlorophenyl)-2-morpholinyl]ethyl]-4-piperidinyl)-2-methylpropanamide], were evaluated. SSR240600 inhibited the binding of radioactive substance P to tachykinin NK1 receptors in human lymphoblastic IM9 cells (K(i) = 0.0061 nM), human astrocytoma U373MG cells (K(i) = 0.10 nM), and human brain cortex (IC50 = 0.017 nM). It also showed subnanomolar affinity for guinea pig NK1 receptors but was less potent on rat and gerbil NK1 receptors. SSR240600 inhibited [Sar(9),Met(O2)(11)]substance P-induced inositol monophosphate formation in human astrocytoma U373MG cells with an IC50 value of 0.66 nM (agonist concentration of 100 nM). It also antagonized substance P-induced contractions of isolated human small bronchi with a pIC50 value of 8.6 (agonist concentration of 100 nM). The compound was >100- to 1000-fold more selective for tachykinin NK1 receptors versus tachykinin NK2 or NK3 receptors as evaluated in binding and in vitro functional assays. In vivo antagonistic activity of SSR240600 was demonstrated on tachykinin NK1 receptor-mediated hypotension in dogs (3 and 10 microg/kg i.v.), microvascular leakage (1 and 3 mg/kg i.p.), and bronchoconstriction (50 and 100 microg/kg i.v.) in guinea pigs. It also prevented citric acid-induced cough in guinea pigs (1-10 mg/kg i.p.), an animal model in which central endogenous tachykinins are suspected to play a major role. In conclusion, SSR240600 is a new, potent, and centrally active antagonist of the tachykinin NK1 receptor, able to antagonize various NK1 receptor-mediated pharmacological effects in the periphery and in the central nervous system.

Biochemical and pharmacological activities of SSR 146977, a new potent nonpeptide tachykinin NK3 receptor antagonist.

SSR 146977 is a potent and selective antagonist of the tachykinin NK3 receptor. In Chinese hamster ovary cells expressing the human tachykinin NK3 receptor, SSR 146977 inhibited the binding of radioactive neurokinin B to NK3 receptors (Ki = 0.26 nM), senktide (10 nM) induced inositol monophosphate formation (IC50 = 7.8-13 nM), and intracellular calcium mobilization (IC50 = 10 nM). It antagonized [MePhe7]neurokinin B induced contractions of guinea pig ileum (pA2 = 9.07). Senktide (30 nM) induced firing rate increase of noradrenergic neurons in the guinea pig locus coeruleus and dopaminergic neurons in the guinea pig substantia nigra was also blocked by SSR 146977 (50 and 100 nM, respectively). In vivo, in the respiratory system, SSR 146977 inhibited bronchial hyperresponsiveness to acetylcholine, bronchial microvascular permeability hypersensitivity to histamine (doses of 0.1-1 mg/kg i.p.), and cough (doses of 0.03-1 mg/kg i.p.) provoked by citric acid in guinea pigs. In the central nervous system, SSR 146977 inhibited turning behaviour (ID50 = 0.2 mg/kg i.p. and 0.4 mg/kg p.o.) and prevented the decrease of locomotor activity (10 and 30 mg/kg i.p) mediated by the stimulation of NK3 receptors in gerbils. In guinea pigs, SSR 146977 antagonized senktide-induced acetylcholine release in the hippocampus (0.3 and 1 mg/kg i.p) and norepinephrine release in the prefrontal cortex (0.3 mg/kg i.p.). It also prevented haloperidol-induced increase of the number of spontaneously active dopamine A10 neurons (1 and 3 mg/kg i.p.).