The molecular mechanism responsible for the neurodegeneration in Alzheimer disease is not known; however, accumulating evidence suggests that 3-amyloid peptide (A.8P) contributes to this degeneration. We now report that synthetic A3Ps trigger the degeneration of cultured neurons through activation of an apoptotic pathway. Neurons treated with AIIPs exhibit morphological and biochemical characteristics of apoptosis, including membrane blebbing, compaction of nuclear chromatin, and internucleosomal DNA fragmenta- This idea is consistent with the fact that cultured cells that express a familial AD-linked mutated form of A,8PP produce severalfold more APP than cells expressing the normal A,8PP

Activation of brain ␣7 nicotinic acetylcholine receptors (␣7 nAChRs) has broad therapeutic potential in CNS diseases related to cognitive dysfunction, including Alzheimer's disease and schizophrenia. In contrast to direct agonist activation, positive allosteric modulation of ␣7 nAChRs would deliver the clinically validated benefits of allosterism to these indications. We have generated a selective ␣7 nAChR-positive allosteric modulator (PAM) from a library of GABA A receptor PAMs. Compound 6 (N-(4-chlorophenyl)-␣-[[(4-chlorophenyl)amino]methylene]-3-methyl-5-isoxazoleacet-amide) evokes robust positive modulation of agonist-induced currents at ␣7 nAChRs, while preserving the rapid native characteristics of desensitization, and has little to no efficacy at other ligand-gated ion channels. In rodent models, it corrects sensory-gating deficits and improves working memory, effects consistent with cognitive enhancement. Compound 6 represents a chemotype for allosteric activation of ␣7 nAChRs, with therapeutic potential in CNS diseases with cognitive dysfunction.cognition ͉ ion channels ͉ memory ͉ nicotine ͉ schizophrenia

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Vanilloids such as capsaicin have algesic properties and seem to mediate their effects via activation of the vanilloid receptor 1 (VR1), a ligand-gated ion channel highly expressed on primary nociceptors. Although blockade of capsaicin-induced VR1 activation has been demonstrated in vitro and in vivo with the antagonist capsazepine, efficacy in rat models of chronic pain has not been observed with this compound. Here, we describe the in vitro pharmacology of a highly potent VR1 antagonist, N-(4-tertiarybutylphenyl)-4-(3-chloropyridin-2-yl)tetrahydropyrazine-1(2H)-carbox-amide (BCTC). Similar to capsazepine, this compound inhibits capsaicin-induced activation of rat VR1 with an IC 50 value of 35 nM. Interestingly however, BCTC also potently inhibits acid-induced activation of rat VR1 (IC 50 value of 6.0 nM), whereas capsazepine is inactive. Similarly, in the rat skin-nerve preparation both BCTC and capsazepine block capsaicin-induced activation, whereas the response to acidification is inhibited by BCTC, but not by capsazepine. Specificity for VR1 was demonstrated against 63 other receptor, enzyme, transporter, and ion channel targets. BCTC was orally bioavailable in the rat, demonstrating a plasma half-life of ϳ1 h and significant penetration into the central nervous system. Thus, BCTC is a high potency, selective VR1 antagonist that, unlike capsazepine, has potent blocking effects on low pH-induced activation of rat VR1. These properties make it a more suitable candidate than capsazepine for testing the role played by VR1 in rat models of human disease.

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A series of 1,2,3,4-tetrahydroquinoline-2,3,4-trione 3-oximes (QTOs) was synthesized and evaluated for antagonism of NMDA receptor glycine site. Glycine site affinity was determined using a [3H]DCKA binding assay in rat brain membranes and electrophysiologically in Xenopus oocytes expressing 1a/2C subunits of cloned rat NMDA receptors. Selected compounds were also assayed for antagonism of AMPA receptors in Xenopus oocytes expressing rat brain poly-(A)+RNA. QTOs were prepared by nitrosation of 2,4-quinolinediols. Structure-activity studies indicated that substitutions in the 5-, 6-, and 7-positions increase potency, whereas substitution in the 8-position causes a decrease in potency. Among the derivatives evaluated, 5,6,7-trichloro-QTO was the most potent antagonist with an IC50 of 7 nM in the [3H]DCKA binding assay and a Kb of 1-2 nM for NMDA receptors expressed in Xenopus oocytes. 5,6,7-Trichloro-QTO also had a Kb of 180 nM for AMPA receptors in electrophysiological assays. The SAR of QTOs was compared with the SAR of 1,4-dihydroquinoxaline-2,3-diones (QXs). For compounds with the same benzene ring substitution pattern, QTOs were generally 5-10 times more potent than the corresponding QXs. QTOs represent a new class of inhibitors of the NMDA receptor which, when appropriately substituted, are among the most potent glycine site antagonists known.

A series of bis(phenylalkyl)amines, structural analogues of ifenprodil and nylidrin, were synthesized and tested for antagonism of N-methyl-D-aspartate (NMDA) receptors. Potency and subunit selectivity were assayed by electrical recordings in Xenopus oocytes expressing three binary combinations of cloned rat NMDA receptor subunits: NR1A expressed in combination with either NR2A, NR2B, or NR2C. The bis(phenylalkyl)amines were selective antagonists of NR1A/2B receptors. Assayed under steady-state conditions, the most potent of these, N-[2-(4-hydroxyphenyl)ethyl]-5-phenylpentylamine hydrochloride (20), has an IC50 value of 8 nM and >1000-fold selectivity with respect to NR1A/2A and NR1A/2C receptors. The structure-activity relationship of the bis(phenylalkyl)amine series indicates that the piperidine ring and alkyl chain substitutions common to NR2B-selective antagonists such as ifenprodil, CP 101,606, and Ro 25-6981 are not necessary to generate potent and selective ligands. The primary determinants of potency are the phenolic OH group, acting as a hydrogen bond donor, the distance between the two rings, and an electrostatic interaction between the receptor and the basic nitrogen atom. This study provides a framework for designing structurally novel NR2B-selective antagonists which may be useful for treatment of a variety of neurological disorders.

Drugs that antagonize nicotinic acetylcholine receptors (nAChRs) can be used to inhibit nicotine-induced behavior in both humans and animals. The aim of our experiments is to establish a proofof-principle that antagonism of nAChRs by negative allosteric modulation can alter behavior in a relevant animal model of addiction, nicotine self-administration. We have identified a novel, negative allosteric modulator of nAChRs, UCI-30002 [N-(1,2,3,4-tetrahydro-1-naphthyl)-4-nitroaniline], with selectivity for the major neuronal nAChR subtypes over muscle-type nAChRs. After systemic administration, UCI-30002 significantly reduces nicotine self-administration in rats on both fixed ratio and progressive ratio schedules of reinforcement. The minimum effective dose that significantly alters nicotine self-administration corresponds to brain concentrations of UCI-30002 that produce at least 30% inhibition of the major neuronal nAChR subtypes measured in vitro. UCI-30002 has no effect on responding for food reinforcement in rats on either type of schedule, indicating that there is no effect on general responding or natural reward. UCI-30002 represents validation of the concept that negative allosteric modulators may have significant benefits as a strategy for treating nicotine addiction and encourages the development of subtype-selective modulators.Tobacco use is responsible for 5 million deaths annually worldwide, and it is projected that half of all current smokers will die prematurely from illnesses related to their addiction (World Health Organization, 2005). In a 2000 United States poll, 70% of adult smokers wanted to quit, and 41% had tried to quit within the preceding year (Centers for Disease Control, 2002). Unfortunately, the prolonged abstinence rate of unaided smoking cessation can be as low as 3 to 5% (Hughes et al., 2004).The action of nicotine at nAChRs lies at the core of nicotine addiction, and a variety of drugs represent clinical validation of nAChRs as a target for smoking cessation therapeutics. The three therapeutic strategies approved by the Food and Drug Administration for smoking cessation are the ␣4␤2 partial agonist varenicline (Chantix), the nicotine replacement therapies (patch, gum, etc.), and the atypical antidepressant bupropion (Zyban). Varenicline and the nicotine replacement therapies are thought to partially replicate the activating or desensitizing actions of nicotine at nAChRs observed when smoking (Coe et al., 2005). Bupropion is an inhibitor of nAChRs (Slemmer et al., 2000) but also increases dopamine levels in the nucleus accumbens (Nomikos et al., 1989(Nomikos et al., , 1992.Ligands that act at nAChRs have been identified with competitive mechanisms of action such as varenicline (Coe et al., 2005) or erysodine (Mansbach et al., 2000) and with noncompetitive mechanisms such as bupropion (Slemmer et al., 2000) or crystal violet (Arias et al., 2006). Allosteric modulators are a class of noncompetitive ligands that act on a separate, distinct site from the agonist (orthosteric) bindi...