ICV galanin-like peptide stimulates non-contact erections but not touch-based erections in adult, sexually experienced male rats.

ABSTRACT

Galanin-like peptide (GALP) is a neuropeptide transcribed only within the arcuate nucleus of the hypothalamus and is thought to be a mediator between energetics and reproductive function. Intracerebroventricular (ICV) injection of GALP is known to have effects on feeding, and to significantly increase gonadotropin releasing hormone- (GnRH-) mediated luteinizing hormone (LH) secretion. Furthermore, ICV GALP is known to stimulate fos production in the medial pre-optic area (mPOA) and to a lesser extent, the paraventricular nucleus (PVN). ICV injection of 5.0nmol GALP profoundly stimulates male rat sexual behavior. It is not known if GALP's effects on sex behavior are due to an increase in appetitive or mechanical (erectile) aspects of male sexual behavior. To determine this, sexually experienced male rats were cannulated in the lateral ventricle and injected with 5.0nmol GALP or vehicle. Immediately after injections, male rats were placed in an arena connected to a second arena via a tube with a fan. The second arena contained a steroid-primed female and her bedding. The male rat had olfactory but not visual or tactile contact with the female. We analyzed the amount of time the male rats spent investigating the air intake and the number of non-contact erections (NCEs) in a 30minute test. ICV GALP significantly (p<0.05) increased both the amount of time of olfactory investigations and NCEs compared to vehicle. In a second set of animals, we tested if ICV GALP could stimulate touch-based erections. GALP had no significant effect on touch-based erections compared to vehicle. These data suggest that GALP's activation of fos within the mPOA is indicative of its action to stimulate the appetitive aspects of male sexual behavior.