RAPID KINETICS OF 2ND MESSENGER FORMATION IN OLFACTORY TRANSDUCTION

OLFACTORY transduction is thought to be mediated by a membrane-bound receptor protein initiating a multistep reaction cascade which ultimately leads to a depolarizing generator current1,2. There is considerable evidence for the involvement of adenylate cyclase in vertebrate olfactory transduction3-6, and some data indicate that phospholipase C may have a central role in insect olfaction7. However, one must show that odorants not only stimulate enzyme activity but also induce changes in concentrations of relevant second messengers. One important criterion for a candidate second messenger of chemo-electrical transduction is that its formation must precede the onset of the odorant-induced membrane permeability changes which proceed on a subsecond time-scale8. Here we report an odorant-induced, transient accumulation of cyclic AMP in isolated olfactory cilia from rats, and the generation of inositol trisphosphate in antennal preparations from insects, both of which show subsecond time courses that are sufficiently rapid to mediate the odorant-regulated permeability of olfactory receptor cells. © 1990 Nature Publishing Group.