Sequential transitions of male sexual behaviors driven by dual acetylcholine-dopamine dynamics

The neural mechanisms underlying the sequential transitions of male sexual behaviors, including mounting, intromission, and ejaculation, remain largely unexplored. Here, we report that acetylcholine (ACh)-dopamine (DA) dynamics in the ventral shell of the nucleus accumbens (vsNAc) regulate these sexual transitions in male mice. During intromission, the vsNAc displays a unique pattern of dual ACh-DA rhythms, generated by reciprocal regulation between ACh and DA signaling via nicotinic ACh receptors (nAChRs) and DA D2 receptors (D2Rs). Knockdown of choline acetyltransferase (ChAT) or D2R in the vsNAc diminishes the occurrence of intromission and ejaculation. Optogenetic manipulations demonstrated that DA signaling maintains sexual behaviors by suppressing D2R^vsNAc neurons. Moreover, ACh signaling promotes the initiation of mounting and intromission and facilitates the intromission-ejaculation transition by inducing a slowdown in DA rhythm. Together, these findings reveal that coordinated ACh-DA dynamics in the vsNAc play a critical role in orchestrating the sequential transitions of male sexual behaviors.