BEHAVIORAL INTERACTIONS HAVE RAPID EFFECTS ON IMMUNOREACTIVITY OF PROHORMONE AND GONADOTROPIN-RELEASING-HORMONE PEPTIDE

The nervous system responds to both internal and external cues, integr ating these signals to coordinate behavior and physiology. Mating inte ractions can promote dramatic changes in neuroendocrine cells which tr igger successful copulation, ovulation, fertilization, and pregnancy. The neurons that transduce behavioral cues into neuroendocrine signals are distributed in a loose continuum along the medial ventral forebra in where they produce and secrete gonadotropin-releasing hormone (GnRH ). In the past we have reported changes in GnRH-immunoreactive (GnRH-i r) cell numbers in brains of female musk shrews sacrificed during, and after, brief mating interactions. The purpose of the current study wa s twofold: first to determine which aspect of intracellular GnRH produ ction is stimulated by behavioral interactions; second, to characteriz e the specific aspects of the social exchange that trigger GnRH produc tion. We report that 1 h after copulation the production of proGnRH pr otein is stimulated. Non-copulatory behavioral interactions resulted i n a rapid decrease in the numbers of neurons containing GnRH-ir peptid e. This change was accompanied by an increase in the GnRH-ir fibers in the median eminence, but no surge in luteinizing hormone. These data suggest that behavioral interactions stimulate release of mature GnRH peptide from cell bodies followed by accumulation of available GnRH in cell terminals. Copulation triggers increased production of proGnRH i n cell bodies. The data highlight the usefulness of behavioral paradig ms for the examination of the dynamics of neuropeptide production. (C) 1997 Elsevier Science B.V.