Nicotine acts on nicotinic acetylcholine receptors, specifically the α3β4 ganglion type nicotinic receptor, present in the autonomic ganglia and adrenal medulla, and a central nervous system (CNS) α4β2 nicotinic receptor. In small concentrations, nicotine increases the activity of these cholinergic receptors and indirectly on a variety of other neurotransmitters such as dopamine.

By binding to nicotinic acetylcholine receptors, nicotine increases the levels of several neurotransmitters – acting as a sort of "volume control". It is thought that increased levels of dopamine in the reward circuits of the brain are a major contributor to the apparent euphoria and relaxation, and addiction caused by nicotine consumption. Nicotine-induced dopamine release occurs via the cholinergic–dopaminergic reward link, which is mediated by the neuropeptide ghrelin in the ventral tegmentum

It also contains the monoamine oxidase inhibitors harman and norharman.[33] These beta-carboline compounds significantly decrease MAO activity in smokers.[33][34] MAO enzymes break down monoaminergic neurotransmitters such as dopamine, norepinephrine, and serotonin.