A transient, RCK4-like K+ current in cultured Xenopus olfactory bulb neurons.
A transient K+ current in cultured olfactory bulb neurons of Xenopus tadpoles was studied using the whole-cell patch-clamp technique. The current, which was resistant to 80 mM tetraethylammoniumchloride (TEA) and 10 nM charybdotoxin but blocked by 5 mM 4-aminopyridine (4-AP), activated between -60 and -40 mV and showed time- and voltage-dependent inactivation. Its peak amplitude was nearly independent of the extracellular K+ concentration ([K+]o) in the range of 0.05 to 10 mM, indicating that its conductance increased upon increasing [K+]o. The transient K+ current showed a slow recovery from inactivation with the time for half-maximum recovery from a conditioning pulse to 80 mV for 1 s varying from 100 ms to 500 ms. Complete recovery required as much as 5-10 s at -80 mV, but could be speeded up at hyperpolarized potentials. The current resembles the RCK4 (Kv1.4) current of rat neurons except that its recovery from inactivation was independent of [K+]o. High-frequency stimulation (20-67 Hz) of the neurons with short (5 ms) voltage pulses resulted in a frequency-dependent, progressive inactivation of the transient K+ current. This suggests that, during phasic responses of olfactory bulb neurons, inactivation of the transient K+ current occurs and may lead to lengthening of action potentials and facilitation of synaptic transmission.
Engel
J
J
Physiologisches Institut, Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany.
Rabba
J
J
Schild
D
D
D000200:Action Potentials / Q000187:drug effects; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000378:metabolism*; D009830:Olfactory Bulb / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014982:Xenopus laevis
D000631:Aminopyridines; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D018999:Charybdotoxin; C076184:BAK4 protein, Bos taurus; D019789:Tetraethylammonium; D011188:Potassium