Sensory mediation of female-male mounting in the rat: I. Role of olfactory cues

Previous research has shown that olfactory cues mediate the mounting of female rats by male or other female rats. The present study examined whether olfactory cues might mediate the mounting of castrated, sexually inactive male rats by sexually receptive female rats (female-male mounting, or FMM). The effects of olfactory impairment, created by either olfactory bulbectomy (OBx) or olfactory occlusion (OOc), on FMM were investigated. Ovariectomized, hormone-primed female rats were given either OBx (OBx+) or sham (OBx−) surgeries. OBx+ females did not engage in any FMM after surgery, whereas sham-operated females continued to mount at baseline levels. This effect was replicated using OOc, a reversible form of olfactory impairment that involves the cannulation of the nasal cavity with a flexible tube. Females were either given the OOc surgery (OOc+), the OOc surgery with the tube removed immediately after placement (OOc−), or sham surgery in which the animal was only anesthetisized. OOc+ females, like OBx+ females, did not display FMM, whereas both control groups continued to mount at baseline levels. The effect of prior experience with FMM was also examined. Females were given either 0 or 5 encounters with castrated males prior to OBx+, OOc+, or OOc− surgeries. OBx+ and OOc+ females did not mount, regardless of prior mounting experience. These data indicate that the olfactory sense is a prime mediator of FMM, and that prior mounting experience does not offset the disruption of FMM caused by the elimination of olfactory cues.