Revisiting medial preoptic area plasticity induced in male mice by sexual experience

Abstract

Sexual experience in male rodents, induced by a first exposure to a receptive female, improves efficiency of following copulations. In mice, the mechanisms supporting this improvement are poorly understood. We characterized molecular modifications of the mouse hypothalamic medial preoptic area (mPOA), the main integrative structure for male sexual behaviour, after a single mating event. This paradigm induced long-lasting behavioural improvements and mPOA morphological changes, evidenced by dendritic spine maturation and an increase in the acetylated and tri-methylated forms of histone H3. Ejaculation affected testosterone, progesterone and corticosterone levels in both naive and experienced mice, but sexual experience did not modify basal plasma or hypothalamic levels of steroids. In contrast to studies carried out in rats, no changes were observed, either in the nitrergic system, or in sex steroid receptor levels. However, levels of glutamate- and calcium-associated proteins, including PSD-95, calbindin and the GluN1 subunit of the NMDA receptor, were increased in sexually experienced male mice. The Iba-1 microglial marker was up-regulated in these animals suggesting multicellular interactions induced within the mPOA by sexual experience. In conclusion, plasticity mechanisms induced by sexual experience differ between rat and mouse, even if in both cases they converge to potentiation of the mPOA network.

Glutamate in Male and Female Sexual Behavior: Receptors, Transporters, and Steroid Independence

“…These include (1) an increased GluN1 surface and intracellular expression 1 day after mating, (2) increased intracellular GluA2 1 week after, and (3) increased surface GluA2 expression 1 month after. Consistent with these results, Western blotting from sexually experienced male C57Bl/6J mice revealed an increase in GluN1 (Jean et al, 2017). In the case of manipulating GluRs, one study directly compared the effects between sexually naïve and sexually experienced rodents (Vigdorchik et al, 2012).…”

Cellular Composition of the Preoptic Area Regulating Sleep, Parental, and Sexual Behavior

“…MPOA neurons also mediate experience-dependent sexual arousal. Sexual experience facilitates all components of mating behaviors, and this facilitation is thought to be mediated by experience-induced changes in MPOA neurons, such as synaptic plasticity ( Jean et al, 2017 ), dopamine sensitivity ( McHenry et al, 2012 ; Nutsch et al, 2016 ), oxytocin sensitivity ( Gil et al, 2013 ), and neuropeptide precursor expression ( Maejima et al, 2018 ).…”

Both neural and global androgen receptor overexpression affect sexual dimorphism in the mouse brain

“…Finally, because the CALB‐SDN was measured in a group of mice distinct from that used for the other dimorphisms, which had acute (90 minutes prior) exposure to sexual odours, it is important to consider whether this olfactory stimulus might have had morphological effects in the CALB‐SDN. It is certainly the case that social stimuli, including the availability of social or sexual partners, can affect morphological features of sexually dimorphic structures in rodents (but see also other studies), making this a plausible mechanism. However, it is unclear whether pheromone exposure per se would be sufficient for this because non‐contact exposure to sexual partners did not affect morphology of SNB motoneurones .…”

“…Furthermore, the acute time course is inconsistent with the chronic paradigms used in these studies. Finally, on principle, 90 minutes is sufficient for measurable alterations in immediate early gene expression, whereas mating requires longer than 90 minutes to cause morphological change in mPOA neurones, and it appears insufficient for alterations in cell number (as might occur in this case by alterations in CALB immunoreactivity), which generally result from longer‐term hormone action. As such, although this may be a contributing factor, it is unlikely to be a significant contributor to the results.…”