Intracellular recordings from two cell types in an in vitro preparation of the salamander olfactory epithelium.

Two electrophysiologically distinct cell types were found with intracellular recordings for the first time in an in vitro preparation of the olfactory epithelium of the salamander, Ambystoma tigrinum. Intracellular recordings showed that Type I cells did not discharge action potentials but had high resting membrane potentials (-50 to -104 mV) and relatively low input resistances. Type II cells had resting membrane potentials of -24 to -52 mV, high input resistances, and discharged upon penetration and to depolarizing current steps. The discharge pattern of Type II cells showed the following characteristics: (1) decreased spike latency and increased discharge frequency with increasing current step intensity; (2) relatively slowly adapting spike trains; and (3) varying spike amplitude during repetitive discharges. The superficial location in the epithelium of the Type I cells implies that they may be sustentacular cells with glial-like electrophysiological properties. The Type II cells are presumably olfactory receptor cells, based on the characteristics of their spike discharge to depolarizing current and their intermediate location within the olfactory epithelium.