5-Hydroxytryptamine (5-HT) 2C receptor agonists hold promise for the treatment of obesity. In this study, we describe the in vitro and in vivo characteristics of lorcaserin [(1R)-8-chloro-2,3,4,5-tetrahydro-1-methyl-1H-3 benzazepine], a selective, high affinity 5-HT 2C full agonist. Lorcaserin bound to human and rat 5-HT 2C receptors with high affinity (K i ϭ 15 Ϯ 1 nM, 29 Ϯ 7 nM, respectively), and it was a full agonist for the human 5-HT 2C receptor in a functional inositol phosphate accumulation assay, with 18-and 104-fold selectivity over 5-HT 2A and 5-HT 2B receptors, respectively. Lorcaserin was also highly selective for human 5-HT 2C over other human 5-HT receptors (5-HT 1A , 5-HT 3 , 5-HT 4C , 5-HT5 5A , 5-HT 6 , and 5-HT 7 ), in addition to a panel of 67 other G protein-coupled receptors and ion channels. Lorcaserin did not compete for binding of ligands to serotonin, dopamine, and norepinephrine transporters, and it did not alter their function in vitro. Behavioral observations indicated that unlike the 5-HT 2A agonist (Ϯ)-1-(2,5-dimethoxy-4-phenyl)-2-aminopropane, lorcaserin did not induce behavioral changes indicative of functional 5-HT 2A agonist activity. Acutely, lorcaserin reduced food intake in rats, an effect that was reversed by pretreatment with the 5-HT 2C -selective antagonist 6-chloro-5-methyl-1-[6-(2-methylpyridin-3-yloxy)pyridin-3-yl-carbamoyl]indoline (SB242,084) but not the 5-HT 2A antagonist (R)-(ϩ)-␣-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidinemethanol (MDL 100,907), demonstrating mediation by the 5-HT 2C receptor. Chronic daily treatment with lorcaserin to rats maintained on a high fat diet produced dose-dependent reductions in food intake and body weight gain that were maintained during the 4-week study. Upon discontinuation, body weight returned to control levels. These data demonstrate lorcaserin to be a potent, selective, and efficacious agonist of the 5-HT 2C receptor, with potential for the treatment of obesity.Serotonin mediates its physiological effects through at least 14 different receptors. The serotonin 5-HT 2 receptor subfamily contains three distinct receptor subtypes, 5-HT 2A , 5-HT 2B , and 5-HT 2C , all of which share considerable sequence homology (Ͼ80% in transmembrane spanning regions) and activate common signaling pathways, including G q ␣-mediated stimulation of phospholipase-C␤, elevation of intracellular inositol phosphates, and elevation of intracellular calcium (Roth et al., 1998). Human 5-HT 2C receptors are predominately expressed in the CNS, and they are highly enriched in choroid plexus, prefrontal cortex, hippocampus, basal ganglia, and other brain regions associated with the control of mood, cognition, and appetite (Roth et al., 1998). Thus, 5-HT 2C receptors have been proposed as a therapeutic target for the treatment of CNS disorders, including epilepsy, obsessive compulsive disorder, Parkinson's disease, schizophrenia, depression and anxiety, sleep disorders, and drug abuse (Tecott et al

Vasopressinergic (VP) neurons in the bed nucleus of the stria terminalis (BNST) of the rat are regulated by gonadal steroids. Gonadectomy causes the projections of the BNST to lose their VP immunoreactivity gradually over a period lasting more than 2 months. Here we have compared the rate of decline of VP mRNA and VP immunoreactivity in the BNST of adult male rats following castration. In experiment 1, the peak number of VP-immunoreactive cells and the level of VP gene expression were compared in sham-operated controls and at 1, 3, or 8 weeks postcastration. The number of VP-immunoreactive cells was not decreased at 1 week postcastration but was significantly reduced (p less than 0.0001) at 3 and 8 weeks postcastration. VP gene expression declined more rapidly, and both the total number of labeled cells (p less than 0.0001) and the average number of grains per cell (p less than 0.01) were significantly reduced by 1 week postcastration. No VP-expressing cells were detectable at 3 or 8 weeks. The difference in the rate of decline in the number of cells labeled by the two techniques following castration did not appear to be due to colchicine pretreatment. In experiment 2, VP mRNA in the BNST was compared in sham-operated controls or at 1, 3, or 7 d postcastration. A significant decrease (p less than 0.01) in the average number of grains per cell was detectable by just 1 d following castration, and the number of labeled cells was significantly reduced (p less than 0.001) by 3 d postcastration.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasopressin (AVP) immunoreactivity in cells and projections of the bed nucleus of the stria terminalis (BST) and medial amygdaloid nucleus (MA) depends on gonadal steroids. In addition, the AVP projections from the BST show denser fiber staining in males than in females. To study whether these differences depend on different hormone levels in adulthood, male and female rats were gonadectomized and similarly treated with testosterone for 4 weeks prior to sacrifice. Immunocytochemistry showed that males had significantly more AVP-immunoreactive (AVP-IR) cells in the BST and significantly denser AVP-IR projections from this nucleus to the lateral septum, lateral habenular nucleus, and periaqueductal central gray than did females. The number of AVP-IR cells in the MA nucleus was not statistically different, but denser AVP-IR fiber networks were found in the MA and ventral hippocampus, which receives its input from the MA. No differences were found in the anteroventral portion of the periventricular nucleus and the dorsomedial nucleus of the hypothalamus that receive their AVP innervation from the suprachiasmatic nucleus. These results indicate that the sex difference in the steroid-sensitive AVP pathways depends on other factors besides circulating hormone levels in adulthood.

Summary. Background: Release of serotonin and activation of serotonin 5HT 2A receptors on platelet surfaces is a potent augmentative stimulus for platelet aggregation. However, earlier-generation serotonin receptor antagonists were not successfully exploited as antiplatelet agents, possibly owing to their lack of specificity for the 5HT 2A receptor subtype. Objective: To assess whether targeted inhibition of the serotonin 5HT 2A receptor attenuates recurrent thrombosis and improves coronary patency in an in vivo canine model mimicking unstable angina. Methods: In protocol 1, anesthetized dogs were pretreated with a novel, selective inverse agonist of the 5HT 2A receptor (APD791) or saline. Recurrent coronary thrombosis was then initiated by coronary artery injury + stenosis, and coronary patency was monitored for 3 h. Protocol 2 was similar, except that: (i) treatment with APD791 or saline was begun 1 h after the onset of recurrent thrombosis; (ii) template bleeding time was measured; and (iii) blood samples were obtained for in vitro flow cytometric assessment of platelet responsiveness to serotonin. Results: APD791 attenuated recurrent thrombosis, irrespective of the time of treatment: in both protocols, flow-time area (index of coronary patency; normalized to baseline coronary flow) averaged 58-59% (P < 0.01) following administration of APD791 vs. 21-28% in saline controls. Moreover, the in vivo antithrombotic effect of APD791 was not accompanied by increased bleeding, but was associated with significant and selective inhibition of serotoninmediated platelet activation. Conclusion: 5HT 2A receptor inhibition with APD791, even when initiated after the onset of recurrent thrombosis, improves coronary patency in the in vivo canine model. Keywords: angina, platelets, serotonin, thrombosis.The pathogenesis of platelet-mediated coronary artery thrombosis is complex, with multiple in vivo agonists playing important causal and contributory roles [1,2]. Current clinical therapies target either cyclo-oxygenase 1, the ADP P2Y 12 receptor, or the glycoprotein (GP) IIb/IIIa receptor [3]. However, these therapies, even in combination, are not fully effective in preventing major thrombotic events [3], and are associated with an increase in bleeding [4].Release of serotonin from platelet dense granules and activation of serotonin receptors on platelet surfaces has long been recognized to serve as a potent augmentative stimulus for platelet aggregation [5][6][7][8]. Clinical application of serotonin receptor antagonists for the prevention of thrombotic coronary events has, however, been confounded by their lack of selectivity for the 5HT 2A receptor (i.e. the serotonin receptor subtype expressed on platelets) [9,10]. Accordingly, our aim was to assess the efficacy of APD791 (Arena Pharmaceuticals, Inc., San Diego, CA, USA), a newly developed, potent and highly selective inverse agonist of the 5HT 2A receptor [9], in a well-established preclinical canine model of recurrent thrombosis mimicking unstable angina [11][12][13][14][...

APD334 was discovered as part of our internal effort to identify potent, centrally available, functional antagonists of the S1P 1 receptor for use as next generation therapeutics for treating multiple sclerosis (MS) and other autoimmune diseases. APD334 is a potent functional antagonist of S1P 1 and has a favorable PK/PD profile, producing robust lymphocyte lowering at relatively low plasma concentrations in several preclinical species. This new agent was efficacious in a mouse experimental autoimmune encephalomyelitis (EAE) model of MS and a rat collagen induced arthritis (CIA) model and was found to have appreciable central exposure.