Activation of Kiss1 neurons in the preoptic hypothalamus stimulates testosterone synthesis in adult male mice

Kisspeptin-expressing neurons in the rostral periventricular region of the third ventricle (RP3V) play an essential role in female reproduction. However, adult male mice were reported to have very few Kisspeptin-expressing neurons in the RP3V compared to females. This led to the hypothesis that Kiss1 RP3V neurons are responsible for the ability of females, but not males, to generate a surge of LH, triggering ovulation and steroid synthesis in the female. Using mouse genetics and cell type-specific gene expression analysis, we show that male mice harbor almost as many Kiss1 RP3V neurons as the female and that gene expression in these neurons is very similar. Specific activation of male Kiss1 RP3V neurons expressing viral-encoded hM3Dq caused a surge in serum testosterone levels. These results demonstrate that Kiss1 RP3V neurons are present in the adult male and fully capable of regulating the hypothalamic/pituitary/gonadal axis. We suggest that these neurons may continue to play a role in reproductive behavior in adult male mice. Overall design: Examination of Kiss1 neuron gene expression in 2 different hypothalamic nuclei, ARC and AVPV/RP3V, in both females and males.