TAAR1 agonists for nicotine addiction

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ABSTRACT Tobacco smoking remains a major public health concern globally. Although there are FDA-approved therapeutic options available, they are far from adequate to maintain long-term smoking abstinence in most smokers. Thus, discovering novel efficacious pharmacotherapies to aid in smoking cessation remains an urgent clinical need. Nicotine, the major component in tobacco that is responsible for tobacco addiction, stimulates the mesolimbic dopaminergic system via activating nicotinic acetylcholine receptors (nAChRs). Nicotine replacement therapy and the nAChR partial agonist varenicline have achieved limited clinical success by directly modulating the central nAChRs. Indirect modulation of dopaminergic system by non-dopaminergic mechanism may also be able to modulate the addiction-related effects of nicotine. Trace amine associated receptor 1 (TAAR1) has emerged as a novel target for the development of potential pharmacotherapy to treat drug addiction. In particular, our preliminary data have shown that acute TAAR1 agonist treatment is able to reduce some addiction-related effects of nicotine. The objective of the present application is to systematically assess the therapeutic potential of TAAR1 agonists on nicotine addiction. Three Specific Aims are proposed: Aim 1 will examine the effects of repeated TAAR1 agonists (full agonist RO5166017 and partial agonist RO5263397) treatment on nicotine reinforcement using a short-access (1 hour) nicotine self-administration paradigm; Aim 2 will examine the effects of TAAR1 agonists on the reinstatement and incubation of nicotine- seeking behavior in rats with a long-access (21 hours) nicotine self-administration history; Aim 3 will examine the effects of TAAR1 agonists on nicotine withdrawal in rats with a long-access (21 hours) nicotine self- administration history. Collectively, the proposed studies systematically evaluate the effects of TAAR1 agonists on four critical aspects of nicotine addiction (e.g., reinforcing effects, reinstatement, incubation and withdrawal symptoms), each of which is thought to contribute significantly to nicotine dependence and relapse. Successful execution of the proposed studies will confirm the essential role TAAR1 in mediating nicotine addiction and provide critical preclinical evidence in support of developing TAAR1 agonists are novel pharmacotherapy for smoking cessation.