Sequential Transitions of Male Sexual Behaviors Driven by Dual Acetylcholine-Dopamine Dynamics

Abstract

In mammals, males execute a stereotypical and organized sequence of sexual behaviours, such as mounting, intromission, and ejaculation, to successfully complete copulation. However, the neural mechanisms that govern the sequential transitions of male copulatory behaviours remain unclear. Here, we report that dopamine (DA) and acetylcholine (ACh) dynamics in the ventral shell of the nucleus accumbens (vsNAc) closely align with serial transitions of sexual behaviours in male mice. In particular, the vsNAc exhibits a unique pattern of 1.5–2.2 Hz dual ACh-DA rhythms that correspond to the pelvic thrust rhythm during intromission. The dual ACh-DA rhythms are generated locally by reciprocal regulation between ACh and DA signalling via nicotinic acetylcholine (nAChR) and dopamine D2 (D2R) receptors, respectively. Knockdown of choline acetyltransferase (ChAT) and D2R expression in the vsNAc diminishes intromission and ejaculation. We showed that ACh signalling promotes the initiation of intromission, whereas DA signalling sustains intromission by inhibiting the activities of D2R-expressing neurons in the vsNAc. Moreover, optogenetic activation of ChATvsNAcneurons during intromission slows down the DA rhythm, a specific activity signature that precedes ejaculation, and leads to immediate ejaculation. Taken together, dual ACh-DA dynamics in the vsNAc coordinate sequential transitions of male copulatory behaviours from intromission to ejaculation.