Intra-hypothalamic circuit orchestrates β-endorphin release following coital ejaculation in male mice
Survey-based evidence suggests that men experience a distinct post-ejaculation affective state1,2, marked by intense pleasure sometimes compared to the euphoric rush from intravenous injection of opioid drugs such as heroin3. However, the intrinsic neural circuit mechanisms underlying the ejaculation-triggered affective state remain unclear. Here, we discovered that Calbindin1-expressing (Calb1+) neurons in the preoptic area (POA) of the hypothalamus, an evolutionarily conserved regulatory region for male mating behavior4, are specifically activated during ejaculation in male mice. Inhibiting POA Calb1+ neurons prolongs mating and delays ejaculation. Importantly, POA Calb1+ neurons transmit the ejaculation signal and activate proopiomelanocortin-expressing (Pomc+) neurons in the arcuate nucleus of the hypothalamus, which show robust and sustained activity lasting for tens of seconds, specifically upon ejaculation. This activity is accompanied by elevated levels of {beta}-endorphins5, opioid peptides secreted by Pomc+ neurons, post-ejaculation in male mice. Optogenetic activation of Pomc+ neurons increases {beta}-endorphins levels and conditioned placed preference, similar to ejaculation. Conversely, intracerebroventricular (i.c.v.) infusion of drugs blocking Pomc neuropeptides signaling eliminates ejaculation-conditioned place preference. Collectively, these results elucidate an intra-hypothalamic circuit from POA Calb1+ neurons to arcuate Pomc+ neurons that coordinate {beta}-endorphin release with ejaculation, shedding light on the neurobiological basis of the post-ejaculation affective state.