Intensity coding in olfactory receptor cells.

Olfactory receptors code the concentration of stimulating molecules into an impulse frequency message. Patch-clamp recordings have now demonstrated, in the olfactory receptor cell membrane, a number of membrane conductances. Some of them are gated by odorants, in the cilia, and depolarize the cell through cAMP- or IP3-sensitive channels, depending on the species. Other conductances are activated by membrane depolarization and/or an increased intracellular Ca2+ concentration; they participate in oscillating membrane potential changes during impulses and post-spike after-polarizations, and control the repetitive firing. Original data relative to the resting potential and the impulse frequency coding of the odorant concentration are presented.