SCANNING ELECTRON-MICROSCOPY AND GRAMICIDIN PATCH-CLAMP RECORDINGS OFMICROVILLOUS RECEPTOR NEURONS DISSOCIATED FROM THE RAT VOMERONASAL ORGAN

Vomeronasal organs from female rats were dissociated and isolated micr ovillous receptor neurons were studied. The isolated receptor neurons kept the typical bipolar shape which they have in situ as observed by scanning electron microscopy. We applied the perforated patch-clamp te chnique using the cation-selective ionophore gramicidin on freshly iso lated and well differentiated receptor neurons. The mean resting poten tial was -58 +/- 14 mV (n = 39). The contribution of the sodium pump c urrent to the resting potential was demonstrated by lowering the K+ co ncentration in the bath or by application of 100 mu M dihydro-ouabain. The input resistance was in the range of 2-6 G Omega and depolarizing current pulses of a few pA were sufficient to trigger overshooting ac tion potentials. In voltage clamp conditions a fast transient sodium i nward current and a sustained outward potassium current were activated by membrane depolarization. These observations indicate that freshly isolated vomeronasal receptor neurons of rats can be recorded, using g ramicidin, with little modification of the intracellular content. Thei r electrophysiological properties are very similar to those observed i n situ. Four out of eight female vomeronasal receptor cells were depol arized by diluted rat male urine.