After 2–3 weeks in culture, pupal olfactory receptor neurons from the antennae of male Manduca sexta respond to their species-specific sex pheromone by opening cation channels. These pheromone-dependent cation channels are the only channels previously found in cultured olfactory neurons that promote inward currents at membrane potentials more negative than the resting potential. The pheromone-dependent currents depend on external Ca2+ concentration. They are inwardly rectified with 10(−7) mol l-1 external Ca2+ and linear with 6 mmol l-1 external Ca2+. This paper shows that perfusion of cultured olfactory receptor neurons with GTP gamma S, ATP, inositol 1,4,5-trisphosphate or 10(−6) mol l-1 Ca2+ elicits cation currents resembling the pheromone-dependent cation currents in expressing inward rectification with 10(−7) mol l-1 external Ca2+ and being linear at external Ca2+ concentrations of 2 mumol l-1 or more. Stimulation with protein kinase C also elicits cation currents that share properties with the pheromone-dependent cation currents. All agent-induced cation currents appear to depend either directly or indirectly on Ca2+ concentration.

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