Molecular discrimination and transduction in singe olfactory and vomeronasal receptor cells

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In order to clarify the odor specificity of a single olfactory cell, various odorants were applied to single olfactory cells of turtle and frog. The results indicated that a single olfactory cell responds to various odorants. In order to examine roles of cyclic GMP in olfactory transduction, cyclic GMP was injected to turtle olfactory cells. The injection induced inward currents. We concluded that the inward currents were induced via cyclic AMP-dependent channel, indicating that pathway specific to cyclic GMP does not exit in turtle olfactory cells. In order to clarify the transduction mechanism of vomeronasal receptor cells, we applied urine, which contains pheromone(s), to rat female vomeronasal cells. Single vomeronasal cell responded only to one species of urine, indicating that a single vomeronasal cell has high specificity. We identified that active components in urine are peptides with molecular weight below 5000. We also tried to identify second messenger in vomeronasal cells. Injection of cyclic AMP to vomeronasal cells induced no response, but injection of inositol trisphosphate (IP3) induced inward currents. Application of inhibitors for generation of IP3 or a blocker of IP3-gated channel blocked the inward currents, suggesting that IP3 is a second messenger in vomeronasal cells.