| Abstract
| - Using the whole-cell mode of the patch-clamp technique, we recorded action potentials, voltage-activated cationic currents and putative second messenger-activated currents in receptor neurons in the vomeronasal sensory epithelium of female rats. The resting membrane potential and input resistance were −45.5 ± 2.5 mV (mean ± SEM, n = 39) and 1.5 ± 0.2 GΩ (mean ± SEM, n = 37). Current injection of 1-3 pA induced overshooting action potentials. The firing frequency increased with increasing current injections linearly from 1 to 10 pA and reached a plateau at 30 pA, suggesting that rat vomeronasal receptor neurons sensitively elicit action potentials in response to a small receptor potential. Under voltage clamp, voltage-dependent Na+ inward current, inward Ca2+ current, sustained outward K+ current and Ca2+-activated K+-current were identified. Dialysis of D-inositol-1,4,5-trisphosphate (D-IP3) induced inward currents with an increase in membrane conductance in ∼54% of the cells and inward current fluctuations in 15% of the cells. L-IP3 also induced inward currents and current fluctuations in 53 and 13% of the cells respectively. The mean amplitude of inward currents induced by 100 μM D-IP3 and L-IP3 were 84.6 ± 14.0 pA (SEM, n = 82) and 66.1 ± 9.4 pA (SEM, n = 100) respectively. The IP3-induced responses were blocked by elimination of Na+ and Ca2+ in the external solution or application of 10 μM ruthenium red. The present study suggested that IP3-mediated transduction pathways exist in rat vomeronasal receptor neurons. Chem. Senses 22: 93-103, 1997.
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