Chemosensitive conductance and inositol 1,4,5-trisphosphate-induced conductance in snake vomeronasal receptor neurons.
Snake vomeronasal receptor neurons in slice preparations were studied using the patch-clamp technique in the conventional and nystatin-perforated whole-cell configurations. The mean resting potential was approximately -70 mV; the average input resistance was 3 GOmega. Neurons required current injection of only 1-10 pA to display a variety of spiking patterns. Intracellular dialysis of 100 microM inositol 1,4,5-trisphosphate (IP(3)) evoked an inward current in 38% of neurons, with an average peak amplitude of 16.4 +/- 2.8 pA at a holding potential of -70mV. Application of 100 microM 3-deoxy-3-fluoro-D-myo-inositol 1,4,5-trisphosphate (F-IP(3)), a derivative of IP(3), also evoked an inward current in 4/8 (50%) neurons (32.6 +/- 58 pA at -70 mV, n = 4). The reversal potentials of the induced components were estimated to be -14 +/- 5 mV for IP(3) and -17 +/- 3 mV for F-IP(3). Bathing the neurons in 10 microM ruthenium red solution greatly reduced the IP(3)-evoked inward current to 1.6 +/- 1.1 pA at -70 mV (n = 6). With Cs(+)-containing internal solution, neither the Ca(2+)-ATPase inhibitor thapsigargin (1-50 microM) nor the Ca(2+)-ionophore ionomycin (10 microM) evoked a significant current response, suggesting that IP(3) can elicit current response in the neurons without mediation by intracellular Ca(2+) stores. Intracellular application of 1 mM cAMP evoked no detectable current response. Extracellular application of chemoattractant for snakes evoked a very large inward current. The reversal potential of the chemoattractant-induced current was similar to that of the IP(3)-induced current. The present results suggest that IP(3) may act as a second messenger in the transduction of chemoattractants in the garter snake vomeronasal organ.
Taniguchi
M
M
Departments of Anatomy and Cell Biology and. Biochemistry, State University of New York Health Science Center at Brooklyn, NY 11203, USA.
Wang
D
D
Halpern
M
M
D000818:Animals; D002628:Chemoreceptor Cells / Q000502:physiology*; D002630:Chemotactic Factors; D000242:Cyclic AMP / Q000494:pharmacology; D004594:Electrophysiology / Q000379:methods; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology / Q000502:physiology*; D015759:Ionomycin / Q000494:pharmacology; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D015398:Signal Transduction; D012903:Smell / Q000502:physiology*; D012911:Snakes / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology; D019147:Vomeronasal Organ / Q000187:drug effects / Q000502:physiology*
D002630:Chemotactic Factors; D015759:Ionomycin; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP