Sensory responses of olfactory and vomeronasal neurons in does are influenced by buck odors and their reproductive status.

Abstract

In mammals, olfactory communication between conspecifics is crucial in modulating reproductive function. In anestrous does (i.e., female goats), exposure to hair from sexually active bucks (SAB, i.e., male goats) triggers a luteinizing hormone response that may induce ovulation, the "male effect". However, the chemicals in buck hair responsible for this effect and the sensory pathways used by the females to detect this information remain insufficiently understood. In this study, we investigated whether sensory cells from the main olfactory epithelium (MOE) and the vomeronasal organ (VNO) of does respond differently to olfactory stimuli from SAB versus wethers (CAS, i.e., castrated bucks) and how this response is influenced by the female reproductive status (breeding season, anestrous, or ovariectomized (OVX)). To explore this possibility, we stimulated freshly dissociated cells of MOE and VNO cells with chloroform/methanol and aqueous extractions from buck hair, and we assessed cell activation using calcium imaging. Regardless of the extraction method, we observed more cells activated by SAB hair compounds than by those from CAS males. More MOE cells from anestrous were activated by both chloroform and aqueous extracts from SAB than MOE cells from breeding season, or OVX does. Most of these responses originated from non-mature olfactory neurons. These findings suggest that females can discriminate buck sexual activity through sensory detection by the MOE and VNO. The increased response in the MOE to SAB hair compounds during the anestrous period suggests that the MOE may play a more significant role in the "male effect" during this period.