Centrally Active Allosteric Potentiators of the M₄ Muscarinic Acetylcholine Receptor Reverse Amphetamine-Induced Hyperlocomotor Activity in Rats

Abstract

Previous clinical and animal studies suggest that selective activators of M 1 and/or M 4 muscarinic acetylcholine receptors (mAChRs) have potential as novel therapeutic agents for treatment of schizophrenia and Alzheimer's disease. However, highly selective centrally penetrant activators of either M 1 or M 4 have not been available, making it impossible to determine the in vivo effects of selective activation of these receptors. We previously identified VU10010 [3-amino-N-(4-chlorobenzyl)-4, 6-dimethylthieno[2,3-b]pyridine-2-carboxamide] as a potent and selective allosteric potentiator of M 4 mAChRs. However, unfavorable physiochemical properties prevented use of this compound for in vivo studies. We now report that chemical optimization of VU10010 has afforded two centrally penetrant analogs, VU0152099 [3-amino-N-(benzo[d], that are potent and selective positive allosteric modulators of M 4 . VU0152099 and VU0152100 had no agonist activity but potentiated responses of M 4 to acetylcholine. Both compounds were devoid of activity at other mAChR subtypes or at a panel of other GPCRs. The improved physiochemical properties of VU0152099 and VU0152100 allowed in vivo dosing and evaluation of behavioral effects in rats. Interestingly, these selective allosteric potentiators of M 4 reverse amphetamine-induced hyperlocomotion in rats, a model that is sensitive to known antipsychotic agents and to nonselective mAChR agonists. This is consistent with the hypothesis that M 4 plays an important role in regulating midbrain dopaminergic activity and raises the possibility that positive allosteric modulation of M 4 may mimic some of the antipsychotic-like effects of less selective mAChR agonists.To date, five muscarinic acetylcholine receptor (mAChR) subtypes have been identified (M 1 -M 5 ) and play important roles in mediating the actions of ACh in the peripheral and central nervous systems (Wess, 1996). Of these, M 1 and M 4 are the most heavily expressed in the CNS and represent attractive therapeutic targets for cognition, Alzheimer's disease, and schizophrenia (Bymaster et al., 2002;Messer, 2002;Raedler et al., 2007). In contrast, the adverse effects of cholinergic agents are thought to be primarily due to activation of peripheral M 2 and M 3 mAChRs (Bymaster et al., 2003a,b).

Involvement of a Subpopulation of Neuronal M4Muscarinic Acetylcholine Receptors in the Antipsychotic-like Effects of the M1/M4Preferring Muscarinic Receptor Agonist Xanomeline

“…Previous efforts to develop highly selective orthosteric agonists of the individual muscarinic subtypes have not been successful. However, selective positive allosteric modulators of the M 4 mAChR have been developed recently (Brady et al, 2008;Chan et al, 2008), and in preclinical studies, positive allosteric modulation of M 4 mAChR has been shown to attenuate apomorphine-induced deficits in prepulse inhibition (Chan et al, 2008) and amphetamineinduced hyperactivity in rats (Brady et al, 2008), supporting the potential role of the M 4 mAChR as a future target for treatment of psychosis.…”

Parkinson's Disease Therapeutics: New Developments and Challenges Since the Introduction of Levodopa

“…These agents provide new opportunities to determine the physiological roles of individual mAChRs in the basal ganglia circuitry and to assess the antiparkinsonian efficacy of highly selective mAChR antagonists (Conn et al, 2009a, b), but to do so the full specificity profile of these compounds must be characterized in vivo. In this regard, recent in vivo studies indicate that the allosteric modulators display favorable pharmacokinetic properties and bloodbrain barrier permeability, and have confirmed their potential therapeutic benefits in rodent models of Alzheimer's disease and schizophrenia (Caccamo et al, 2006;May et al, 2007;Brady et al, 2008;Chan et al, 2008;Shekhar et al, 2008;Conn et al, 2009a, b;Bridges et al, 2010;Digby et al, 2010 A 2A receptor antagonists (Schwarzschild et al, 2006;Menon and Stacy, 2008;Morelli et al, 2010;Shah and Hodgson, 2010). Adenosine is a ubiquitous purine with signaling properties that mediate its effects through four subtypes of G-protein-coupled adenosine receptors: A 1 , A 2A , A 2B , and A 3 (Schwarzschild et al, 2006;Menon and Stacy, 2008;Morelli et al, 2007Morelli et al, , 2009Morelli et al, , 2010Shah and Hodgson, 2010).…”

Inhibition of 11β–hydroxysteroid dehydrogenase type II selectively blocks the tumor COX-2 pathway and suppresses colon carcinogenesis in mice and humans

“…injection of GA, the animals were sacrificed, and kidneys, colons, and tumors were collected and stored at -80°C. Tissue levels of CS, 11-keto-corticosterone, GA, and GE were measured using high-performance liquid chromatography coupled with electrospray tandem mass spectrometry (53). GA and GE were from Sigma-Aldrich, CS was from ICN Biomedicals, and 11-keto-corticosterone was from Steroids.…”