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

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The synthesis and SAR of a novel 3-benzazepine series of 5-HT2C agonists is described. Compound 7d (lorcaserin, APD356) was identified as one of the more potent and selective compounds in vitro (pEC50 values in functional assays measuring [(3)H]phosphoinositol turnover: 5-HT2C = 8.1; 5-HT2A = 6.8; 5-HT2B = 6.1) and was potent in an acute in vivo rat food intake model upon oral administration (ED50 at 6 h = 18 mg/kg). Lorcaserin was further characterized in a single-dose pharmacokinetic study in rat (t1/2 = 3.7 h; F = 86%) and a 28-day model of weight gain in growing Sprague-Dawley rat (8.5% decrease in weight gain observed at 36 mg/kg b.i.d.). Lorcaserin was selected for further evaluation in clinical trials for the treatment of obesity.

Site-directed and monoclonal antibodies recognizing different extracellular regions of the RI, sodium channel a subunit have been used to determine the sequences that comprise the receptor for a-scorpion toxins by evaluating the effect of antibody on voltage-dependent binding of radiolabeled toxin isolated from Leiurus quinquestriatus to both reconstituted rat brain sodium channel and rat brain synaptosomes. Kinetic studies of the antibody effect are consistent with a slowly reversible competition for the toxin receptor site. Our results suggest that the extracellular loops between segments S5 and S6 of domains I and IV comprise at least part of the a-scorpion toxin receptor site and support the membrane topology models in which domains I and IV are adjacent in the tertiary structure of the channel protein and six transmembrane sequences are contained in each of the four homologous domains.The voltage-dependent sodium channel is an integral plasma membrane protein responsible for the increase in sodium ion permeability during the rapidly rising phase of the action potential of excitable cells (1). The sodium channel isolated from rat brain consists of three nonidentical glycoprotein subunits, a 260-kDa a subunit that is covalently associated with a 33-kDaP2 subunit and noncovalently associated with a 36-kDa ,1 subunit (2, 3). Messenger RNA encoding the a subunit alone can direct the synthesis of functional sodium channels in Xenopus oocytes (4, 5) and mammalian somatic cells (6). Computer analysis and similarity comparisons ofthe primary amino acid sequence of sodium channel a subunits (3) has been used to construct topological models of the a subunit within the plasma membrane having four homologous domains containing six (3) or eight (7, 8) transmembrane segments per domain. a-Scorpion toxin V isolated from the venom of the North African scorpion Leiurus quinquestriatus (LqTx) binds to neurotoxin receptor site 3 on the sodium channel in a voltage-dependent manner (9, 10) and slows or blocks sodium channel inactivation at an extracellular locus (11,12). Photoreactive derivatives of LqTx covalently label the a subunits in neurons. synaptosomes, and purified and reconstituted sodium channels (13-16), and sodium channels expressed from a-subunit mRNA in somatic cells have a functional receptor site for LqTx (6). The site of covalent attachment of photoreactive derivatives to the a subunit has been localized by immunoprecipitation with site-directed antipeptide antibodies to the extracellular loop between proposed transmembrane segments S5 and S6 of domain I (16). In the present experiments, we have analyzed the effects of a series of site-directed antipeptide and monoclonal antibodies (mAbs) on the voltage-dependent binding of LqTx to sodium channels to define regions of the channel structure that are located on its extracellular surface and are required for toxin binding at higher resolution.

Melanin-concentrating hormone (MCH) is a cyclic peptide produced in the lateral hypothalamus. It has been implicated in a number of physiological processes including feeding behavior, energy balance, and the regulation of emotional states. (1-10 mg/kg) significantly reduced immobility time in the forced swimming test in rats, indicating antidepressantlike effects. Both ATC0065 and ATC0175 significantly reversed swim stress-induced anxiety in the elevated plus-maze test in rats and stress-induced hyperthermia in mice. ATC0175 significantly increased social interaction between unfamiliar rats and reduced separation-induced vocalizations in guinea pig pups, indicating anxiolytic potential. In contrast, ATC0065 and ATC0175 did not affect spontaneous locomotor activity or rotarod performance in rats. These findings indicate that ATC0065 and ATC0175 are potent and orally active MCHR1 antagonists with anxiolytic and antidepressant activity in rodents.Melanin-concentrating hormone (MCH) is a cyclic neuropeptide originally isolated from salmon pituitary (Kawaguchi et al., 1983). In mammals, MCH is produced predominantly by neurons in the lateral hypothalamus and zona incerta with extensive projections throughout the brain (Bittencourt et al., 1992). This expression pattern supports a role for MCH in numerous physiological processes including motivated behavior, stress responses, regulation of neuroendocrine function, and feeding.Several groups independently identified a G protein-coupled receptor, SLC-1/GPR24, as an MCH receptor (MCHR1) (Bachner et al., 1999;Chambers et al., 1999;Lembo et al., 1999;Saito et al., 1999;Shimomura et al., 1999), and MCHR2 was identified subsequently on the basis of the sequence homology to MCHR1 Hill et al., 2001;Mori et al., 2001;Sailer et al., 2001). Potential physiological functions of MCHR2 have not been elucidated due to the species-specific expression of the receptor (Tan et al., 2002); therefore, current research has focused on MCHR1.There are several lines of evidence implicating MCHR1 in feeding and energy homeostasis. MCHR1 mRNA is increased Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.