Ultrasensitive pheromone detection by mammalian vomeronasal neurons

The vomeronasal organ (VNO) is a chemoreceptive organ that is thought to tr ansduce pheromones into electrical responses that regulate sexual, hormonal and reproductive function in mammals(1-5). The characteristics of pheromon e signal detection by vomeronasal neurons remain unclear(3,5). Here we use a mouse VNO slice preparation to show that six putative pheromones evoke ex citatory responses in single vomeronasal neurons, leading to action potenti al generation and elevated calcium entry. The detection threshold for some of these chemicals is remarkably low, near 10(-11) M, placing these neurons among the most sensitive chemodetectors in mammals. Using confocal calcium imaging, we map the epithelial representation of the pheromones to show th at each of the ligands activates a unique, nonoverlapping subset of vomeron asal neurons located in apical zones of the epithelium. These neurons show highly selective tuning properties and their tuning curves do not broaden w ith increasing concentrations of ligand, unlike those of receptor neurons i n the main olfactory epithelium. These findings provide a basis for underst anding chemical signals that regulate mammalian communication and sexual be haviour.