SENSITIVITY AND BEHAVIORAL-RESPONSES TO THE PHEROMONE ANDROSTENONE ARE NOT MEDIATED BY THE VOMERONASAL ORGAN IN DOMESTIC PINS

Based largely on results of studies of laboratory rodents, the vomeron asal or accessory olfactory system is believed to function mainly in s ocial communication, mediating the effects of stimuli such as urine or glandular secretions on the behavior or endocrine response of conspec ifics. In the domestic pig (Sus scrofa), the steroid androstenone has been identified as a pheromone that facilitates expression of both am- action to the male and a receptive mating stance in estrous females. T hough the domestic pig is one of the few vertebrate species in which t he identity of a compound that functions as a pheromone is known, the role of the vomeronasal system in domestic pigs has never been investi gated. We have examined the role of the vomeronasal organ in mediating the pheromonal effects of androstenone in pigs. In addition, we have examined the structure of the vomeronasal organ at the gross and light -microscopic levels. The vomeronasal organ appears functional, with se nsory epithelium lining the medial wall, and has access to stimuli fro m both the oral and nasal cavities. To determine whether the vomeronas al organ is necessary for androstenone detection or attraction or rece ptive behavior in female pigs, access to the vomeronasal organ was blo cked with surgical cement, and androstenone detection threshold and se xual behavior were measured. Experimental animals did not differ signi ficantly in androstenone sensitivity, measured behaviorally, from untr eated controls. Vomeronasal organ-blocked animals also did not differ from untreated controls in either androstenone-mediated receptive stan ding behavior or attraction to the odor of androstenone. We conclude t hat in the domestic pig, the vomeronasal organ is not necessary for an drostenone detection or androstenone-mediated sexual behavior in estro us females.