Inositol-1,4,5-trisphosphate induces responses in receptor neurons in rat vomeronasal sensory slices.
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 G omega (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 Ca-(2+)-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 approximately 54% of the cells and inward current fluctuations in 15% of the cell. 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 microM 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 microM ruthenium red. The present study suggested that IP3-mediated transduction pathways exist in rat vomeronasal receptor neurons.
Inamura
K
K
Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Kashiwayanagi
M
M
Kurihara
K
K
D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D005260:Female; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015290:Second Messenger Systems / Q000187:drug effects* / Q000502:physiology; D012964:Sodium / Q000378:metabolism; D019147:Vomeronasal Organ / Q000187:drug effects* / Q000502:physiology
D015544:Inositol 1,4,5-Trisphosphate; D012964:Sodium; D011188:Potassium; D002118:Calcium