These results support further investigation of xanomeline as a novel approach to treating schizophrenia.

We describe a novel corticotropin-releasing factor receptor 1 (CRF 1 ) antagonist with advantageous properties for clinical development, and its in vivo activity in preclinical alcoholism models. 1-10 mg/kg). In contrast, MTIP dose-dependently reversed anxiogenic effects of withdrawal from a 3 g/kg alcohol dose. Similarly, MTIP blocked excessive alcohol self-administration in Wistar rats with a history of dependence, and in a genetic model of high alcohol preference, the msP rat, at doses that had no effect in nondependent Wistar rats. Also, MTIP blocked reinstatement of stress-induced alcohol seeking both in postdependent and in genetically selected msP animals, again at doses that were ineffective in nondependent Wistar rats. Based on these findings, MTIP is a promising candidate for treatment of alcohol dependence.

The findings suggest that EtOH is reinforcing within the posterior VTA of Wistar rats, and the VTA is a functionally heterogeneous structure with regard to EtOH reinforcement.

Three distinct classes of drugs: dopaminergic agonists (such as D-amphetamine), serotonergic agonists (such as LSD), and glutamatergic antagonists (such as PCP) all induce psychotomimetic states in experimental animals that closely resemble schizophrenia symptoms in humans. Here we implicate a common signaling pathway in mediating these effects. In this pathway, dopamine- and an adenosine 3',5'-monophosphate (cAMP)-regulated phospho-protein of 32 kilodaltons (DARPP-32) is phosphorylated or dephosphorylated at three sites, in a pattern predicted to cause a synergistic inhibition of protein phosphatase-1 and concomitant regulation of its downstream effector proteins glycogen synthesis kinase-3 (GSK-3), cAMP response element-binding protein (CREB), and c-Fos. In mice with a genetic deletion of DARPP-32 or with point mutations in phosphorylation sites of DARPP-32, the effects of D-amphetamine, LSD, and PCP on two behavioral parameters-sensorimotor gating and repetitive movements-were strongly attenuated.

Current antipsychotics provide symptomatic relief for patients suffering from schizophrenia and related psychoses; however, their effectiveness is variable and many patients discontinue treatment due to side effects. Although the etiology of schizophrenia is still unclear, a leading hypothesis implicates an imbalanced dopaminergic system. Muscarinic acetylcholine (

The M5 muscarinic receptor is the most recent member of the muscarinic acetylcholine receptor family (M1-M5) to be cloned. At present, the physiological relevance of this receptor subtype remains unknown, primarily because of its low expression levels and the lack of M 5 receptor-selective ligands. To circumvent these difficulties, we used gene targeting technology to generate M 5 receptor-deficient mice (M5R ؊/؊ mice). M5R ؊/؊ mice did not differ from their wild-type littermates in various behavioral and pharmacologic tests. However, in vitro neurotransmitter release experiments showed that M 5 receptors play a role in facilitating muscarinic agonist-induced dopamine release in the striatum. Because M 5 receptor mRNA has been detected in several blood vessels, we also investigated whether the lack of M 5 receptors led to changes in vascular tone by using several in vivo and in vitro vascular preparations. Strikingly, acetylcholine, a powerful dilator of most vascular beds, virtually lost the ability to dilate cerebral arteries and arterioles in M5R ؊/؊ mice. This effect was specific for cerebral blood vessels, because acetylcholine-mediated dilation of extracerebral arteries remained fully intact in M5R ؊/؊ mice. Our findings provide direct evidence that M 5 muscarinic receptors are physiologically relevant. Because it has been suggested that impaired cholinergic dilation of cerebral blood vessels may play a role in the pathophysiology of Alzheimer's disease and focal cerebral ischemia, cerebrovascular M 5 receptors may represent an attractive therapeutic target. M olecular cloning studies have revealed the existence of five molecularly distinct muscarinic acetylcholine receptor subtypes (M 1 -M 5 ) (1, 2). During the past decade, considerable progress has been made in delineating the physiological roles of the M 1 -M 4 muscarinic receptors (3, 4). In contrast, the physiological relevance of the M 5 receptor subtype, which is the most recent member of the muscarinic receptor family to be cloned (5, 6), remains unknown at present (7,8). However, expression of the cloned M 5 muscarinic receptor gene in cultured mammalian cells has shown that the encoded receptor protein is functional and efficiently couples to G proteins of the G q family, similar to the M 1 and M 3 receptor subtypes (5-8).Immunoprecipitation and in situ mRNA hybridization studies have demonstrated the presence of M 5 receptor protein͞mRNA in different areas of the brain including hippocampus, hypothalamus, and distinct midbrain regions (substantia nigra pars compacta and ventral tegmental area) (9-11). However, M 5 receptors are expressed at very low levels, representing less than 2% of the total muscarinic receptor population (M 1 -M 5 ) expressed in the brain (9). Interestingly, the use of highly sensitive reverse transcriptase-PCR (RT-PCR) techniques suggests that M 5 receptors are expressed in all major brain regions (12). More recently, M 5 receptors also have been detected in several peripheral tissues or cells including peripheral blood l...

We recently identified LY2033298 as a novel allosteric potentiator of acetylcholine (ACh) at the M 4 muscarinic acetylcholine receptor (mAChR). This study characterized the molecular mode of action of this modulator in both recombinant and native systems. Radioligandbinding studies revealed that LY2033298 displayed a preference for the active state of the M 4 mAChR, manifested as a potentiation in the binding affinity of ACh (but not antagonists) and an increase in the proportion of high-affinity agonist-receptor complexes. This property accounted for the robust allosteric agonism displayed by the modulator in recombinant cells in assays of [ 35 S]GTPgS binding, extracellular regulated kinase 1/2 phosphorylation, glycogen synthase kinase 3b phosphorylation, and receptor internalization. We also found that the extent of modulation by LY2033298 differed depending on the signaling pathway, indicating that LY2033298 engenders functional selectivity in the actions of ACh. This property was retained in NG108-15 cells, which natively express rodent M 4 mAChRs. Functional interaction studies between LY2033298 and various orthosteric and allosteric ligands revealed that its site of action overlaps with the allosteric site used by prototypical mAChR modulators. Importantly, LY2033298 reduced [ 3 H]ACh release from rat striatal slices, indicating retention of its ability to allosterically potentiate endogenous ACh in situ. Moreover, its ability to potentiate oxotremorine-mediated inhibition of condition avoidance responding in rodents was significantly attenuated in M 4 mAChR knockout mice, validating the M 4 mAChR as a key target of action of this novel allosteric ligand.

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