Single Odors Differentially Stimulate Dual Second Messenger Pathways in Lobster Olfactory Receptor Cells

Quench-flow measurements are used to determine the sub-second kinetics of odor-induced changes in second mes-senger concentrations in lobster olfactory receptor neurons. Individual odors transiently and differentially increase the production of both adenosine CAMP and inositol 1,4,5tris-phosphate (IP,) within 50 msec of odor stimulation. The abil-ity of two different odors to stimulate CAMP and IP, correlates with the odors ’ ability to excite and inhibit receptor cells physiologically. These results strengthen the proposition, heretofore based largely on evidence from cultured cells, that dual second messenger pathways mediate excitatory and inhibitory input to lobster olfactory receptor cells. [Key words: chemical senses, sensory transduction, oi-faction, second messengers, CAMP, inositol 1,4,5-trisphos-phate, lobster] Odors are generally considered to activate olfactory receptor cells through G-protein<oupled receptors that elicit rapid and transient pulses of intracellular second messengers (for recent reviews, see Breer and Boekhoff, 1992; Ronnett and Snyder, 1992; Anholt, 1993). Attention has focused on two second mes-senger pathways, one mediated by adenosine CAMP and the other by inositol 1,4,5trisphosphate (IP,). CAMP- and IP,-me-diated olfactory transduction cascades have been identified in three different species of animals (rat: Boekhoff et al., 1990