ABSTRACT
Reception..................................................................................................... 349 12.4 Pheromonal Transduction Mediated via Phospholipase C in the
Mammalian Vomeronasal System .............................................................. 350 12.5 Pheromonal Transduction Dependent and Independent on TRPC2 ........... 351 12.6 Selective Pheromone Reception in VSNs ................................................... 353 12.7 Pheromone Receptors.................................................................................. 355 12.8 Projection of Pheromonal Information to the AOB .................................... 355 12.9 Interaction between Sexual Behavior and Gonadal Hormones .................. 357 12.10 Functional Changes in Neurons at the AOB Induced by Sexual
Experience ................................................................................................... 358 12.11 Gonadal Hormones Induces Changes in Brain Functions .......................... 358 12.12 Gonadal Hormones Modulate GABAergic Functions ................................ 359
Pheromones affect gonadal functions and sexual behaviors, which are mainly received by the vomeronasal sensory neurons (VSNs) in the vomeronasal organ (VNO). The mechanism of discrimination and transduction in the pheromone reception is simple in contrast to the reception of general odorants in the main olfactory system. Single olfactory sensory neurons respond to various kinds of odorants that have various molecular structures and odor qualities. Most single VSNs, however, receive only one kind of pheromone. In rodents, pheromones are received with two types of pheromone receptors such as VR1s and VR2s, which exist at the upper and lower layers of the vomeronasal sensory epithelium. Binding of pheromones with VR1s and VR2s activates phospholipase C via Gi and Go, respectively, which in turn induces production diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (IP3). DAG activates TRPC2, a TRP channel, which induces depolarization of the VSN. In general, DAG has been considered as only a second messenger inducing depolarization by pheromones. However, in mice lacking TRPC2, 2-heptanone, a mouse pheromone, and urine containing various pheromones of high concentration induced pheromonal responses in the VSN. Dialysis of IP3 into the VSNs of the rat and turtle induced inward currents with increases in membrane conductance. These results suggest that IP3 also plays a role as second messengers in the pheromonal reception.
