SENSITIZATION OF OLFACTORY GUANYLYL CYCLASE TO A SPECIFIC IMPRINTED ODORANT IN COHO SALMON

The role of cGMP in olfactory signaling is not fully understood, but i t is believed to play a modulatory role in intracellular signaling in vertebrate olfactory receptor neurons (ORNs). Here, we present evidenc e that cGMP in ORNs may play an important role in recognition of biolo gically relevant odors and olfactory learning. Specifically, we invest igated the cellular mechanisms underlying olfactory imprinting in salm on. Salmon learn odors associated with their natal site as juveniles a nd later use these odors to guide their homing migration. This imprint ing is believed to involve sensitization of the peripheral olfactory s ystem to specific homestream odorants. We imprinted juvenile salmon to the odorant beta-phenylethyl alcohol (PEA) and examined the sensitivi ty of olfactory adenylyl and guanylyl cyclases to PEA during developme nt. Stimulation of guanylyl cyclase activity by PEA was significantly greater in olfactory cilia isolated from PEA-imprinted salmon compared with PEA-naive fish only at the time of the homing migration, 2 years after PEA exposure. These results suggest that sensitization of olfac tory guanylyl cyclase may play an important role in olfactory imprinti ng by salmon.