MINIREVIEW - BEHAVIORAL-REGULATION OF GONADOTROPIN-RELEASING-HORMONE

GnRH controls the hypothalamic-pituitary-gonadal axis in all vertebrat e species. Yet despite intense efforts, limited progress has been made reward determining how production of this neuropeptide is regulated. An alternative approach to this problem is to study species whose repr oductive status is sensitive to behavioral influences and then to use behavioral interactions to probe the GnRH neuronal system. In this rev iew, data on behaviorally induced alterations in the GnRH system will be presented. In several species of fishes, reproductive status and se x can be altered in adults by changes in the social environment. In th ese fishes, the numbers and size of GnRH-immunoreactive (GnRH-ir) neur ons are modified by an individual's social and sexual status. In the r ing dove, courtship activates ovarian follicular development and stimu lates androgen production in males. During courtship, mast cells conta ining GnRH-like immunoreactivity enter the brain. This finding present s a new avenue for examining behavioral endocrine and immune interacti ons. In the musk shrew, most aspects of female reproduction are activa ted by contact with a male. Interactions with males trigger changes in the numbers of GnRH-ir cells and rapid production of GnRH peptide. Th e use of comparative animal models provides us with new insights into neuronal plasticity, neuroendoimmunology, and reproductive biology.