GONADOTROPIN-RELEASING HORMONE-IMMUNOREACTIVE CELL NUMBERS CHANGE IN RESPONSE TO SOCIAL INTERACTIONS

Puberty is characterized by either a steroid-dependent or independent increase in the production and secretion of neural GnRH. Several measures have been used to assess the pubertal activation of neurons that express GnRH. Some morphological changes in these cells occur at puberty, but no dramatic changes indicative of increases in the synthesis of GnRH have been noted. In the musk shrew, puberty is induced by mating. We hypothesize that because the first mating facilitates the display of female sexual behavior and subsequent ovulation, that mating may have direct and rapid effects on GnRH neurons. Significant changes in the number of GnRH-immunoreactive (GnRH-ir) neurons in the brains of prepubertal virgin females were noted after contact with males. Different populations of GnRH-ir cells were affected by different types of interactions with males. Exposure to an adult male across a wire barrier for 48 h increased the number of GnRH-ir cells in olfactory-related nuclei. Mating increased GnRH-ir cell numbers in olfactory and ventral forebrain regions. Ovulation reduced GnRH-ir cell numbers in several forebrain nuclei. These rapid and quantitative responses of GnRH-ir neurons to social cues allow direct examination of the neuroendocrine changes that occur at puberty.