Blunt olfaction in sexually sluggish male rats

Among the intact male rats, a subpopulation has been found to show little or no sexual behavior, even after experiencing several mating sessions. This study investigated whether sexually sluggish (SS) males show behavioral differences from normal copulatory (NC) males, other than those concerning sexual behavior. The olfactory preference of males was measured through the time spent displaying nose-poking behavior directed at sexually active males and estrous females for odor exploration in a three-chamber apparatus. Both the NC and SS males showed a significant preference for the odor of estrous females compared with that of male odors. However, SS males spent significantly less time nose-poking estrous females than NC males. The food-finding test was performed after overnight fasting. Our findings showed that all the NC males found the buried pellet within 5 min, whereas over 60% of the SS males failed to find it. The males were also tested for their ability to find a buried bag containing soiled bedding from estrous female cages. The bag was found by 80% of NC males, but only by 20% of SS males. Our results suggest that SS and NC male rats differ not only in sexual behavior but also in other functions such as olfaction.