PHEROMONE REGULATED PRODUCTION OF INOSITOL-(1,4,5)TRISPHOSPHATE IN THE MAMMALIAN VOMERONASAL ORGAN

Social behaviors of most mammals are profoundly affected by chemical s ignals, pheromones, exchanged between conspecifics. Pheromones interac t with dendritic microvilli of bipolar neurons in the vomeronasal orga n (VNO). To investigate vomeronasal signal transduction pathways, micr ovillar membranes fi om porcine VNO were prepared. Incubation of such membranes from prepubertal females with boar seminal fluid or urine re sults in an increase in production of inositol-(1, 4, 5)-trisphosphate (IP3). The dose response for IP3 production is biphasic with a GTP-de pendent component at low stimulus concentrations and a nonspecific inc rease in IP3 at higher stimulus concentrations. The GTP-dependent stim ulation is mimicked by GTP gamma S and blocked by GDP beta S. Furtherm ore, the GTP-dependent component of the stimulation of IF, production is sex specific and tissue dependent. Studies with monospecific antibo dies reveal a G alpha(q/11)-related protein in vomeronasal neurons, co ncentrated at their microvilli. Our observations indicate that pheromo nes in boar secretions act on vomeronasal neurons in the female VNO vi a a receptor mediated, G protein-dependent increase in IP3. These obse rvations set the stage for further investigations on the regulation of stimulus-excitation coupling in vomeronasal neurons. The pheromone-in duced IP3 response also provides an assay for future purification of m ammalian reproductive pheromones.