About Varenicline Tartrate Nicotinic Receptor partial agonist Mechanism of Action of Varenicline Tartrate Varenicline is a partial agonist of the ?4?2 subtype of the nicotinic acetylcholine receptor. In addition it acts on ?3?4 and weakly on ?3?2 and ?6-containing receptors. A full agonism was displayed on ?7-receptors. Acting as a partial agonist varenicline binds to, and partially stimulates, the ?4?2 receptor without producing a full effect like nicotine. Thus varenicline does not greatly increase the downstream release of dopamine. Due to its competitive binding on these receptors, varenicline blocks the ability of nicotine to bind and stimulate the mesolimbic dopamine system, akin to the action of buprenorphine in the treatment of opioid addiction. Varenicline also acts as an agonist at 5-HT3 receptors, which may contribute to mood altering effects of varenicline