Intracellular dialysis of cyclic nucleotides induces inward currents in turtle vomeronasal receptor neurons.
Turtle vomeronasal receptor neurons in slice preparations were studied using the patch-clamp technique in the whole-cell and cell-attached configurations. The mean resting potential was -48, and the response to an injected current step consisted of either a single spike or a train of spikes. An injected current of 3-30 pA was required to depolarize the neuron to spike threshold near -50 mV. Voltage-clamped vomeronasal receptor neurons displayed transient inward currents followed by sustained outward currents in response to depolarizing voltage steps. In cell-attached recordings, 10 microM forskolin added to the bath caused a transient increase of spike rate. Intracellular application of cAMP evoked ann inward current in a dose-dependent manner from the neurons voltage clamped at -70 mV; 0.1 mM cAMP was sufficient to elicit an inward current in the neurons. The magnitude of the response to cAMP reached a plateau at 1 mM with an average peak amplitude of 176 +/- 34 pA. Intracellular application of 1 mM cGMP also evoked an inward current with an average peak amplitude of 227 +/- 61 pA. The reversal potentials of the induced components were estimated to be 10 +/- 7 mV for cAMP and -4 +/- 16 mV for cGMP. The reversal potential of the cAMP-induced current in external Cl(-)-free solution was similar to that in normal Ringer's solution, suggesting that Cl- current is not significantly involved in the current. The present results represent the first evidence of cyclic nucleotide-activated conductance in the vomeronasal receptor membranes.
Taniguchi
M
M
Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Kashiwayanagi
M
M
Kurihara
K
K
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D006152:Cyclic GMP / Q000494:pharmacology*; D017551:Microdialysis; D009300:Nasal Septum / Q000033:anatomy & histology*; D018034:Olfactory Receptor Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D014426:Turtles
D005576:Colforsin; D000242:Cyclic AMP; D006152:Cyclic GMP