Vomeronasal system, LHRH, and sex behaviour

Vomeronasal chemosensory input is important for male hamster mating behavior, especially in inexperienced animals. Experiments reviewed here showed that intracerebroventricular injection of luteinizing hormone-releasing hormone (LHRH) substantially restores mating behavior impaired by removal of vomeronasal organs in inexperienced hamsters. An analogue molecule Ac5-10LHRH, which fails to release luteinizing hormone (LH) from the pituitary, has similar behavioural effects. These findings are consistent with the idea that vomeronasal sensory input may trigger intracerebral release of LHRH which then facilitates mating behaviour. Immunocytochemistry for the immediate-early gene-product Fos, used as an indicator of regional brain activation, indicates a selective activation of central vomeronasal pathways during mating behaviour. Chemosensory and other sensory inputs contribute to activation in medial amygdala and bed-nucleus of stria terminalis, but medial preoptic/anterior hypothalamic area activation appears more closely tied to mating behavior itself. Any of these areas may be sites of interaction between vomeronasal chemosensory input and LHRH-containing cells and fibers.