Voltage- and Ca(2+)-gated currents in zebrafish olfactory receptor neurons.
Voltage- and Ca(2+)-gated currents were recorded from isolated olfactory receptor neurons (ORNs) of the zebrafish Danio rerio using the whole-cell voltage-clamp technique. Zebrafish ORNs had an average capacitance of 0.66 pF and an average apparent input resistance of 8.0 G omega. Depolarizing steps elicited transient inward currents followed by outward currents with transient and sustained components. The transient inward current (INa) was sensitive to 1 mumol l-1 tetrodotoxin, activated between -74mV and -64mV, and reached half-maximal conductance at -28 mV. Its peak amplitude averaged -101pA. Steady-state inactivation of INa was half-maximal at an average test potential of -78mV and recovery from inactivation proceeded with two time constants averaging 23 ms and 532 ms. A sustained, Co(2+)-sensitive current (ICa) activated between -44mV and -34mV and reached a peak amplitude averaging -9pA at -14mV. Outward currents were carried by K+, based on the reversal potentials of tail currents, and consisted of a Ca(2+)-dependent K+ current, a delayed rectifier current (IDR) and a transient K+ current (IA). The Ca(2+)-dependent K+ current (IK(Ca)) activated between -44mV and -34mV, whereas IDR and IA activated between -34mV and -24mV. In summary, zebrafish ORNs possess a complement of gated currents similar but not identical to that of ORNs from other vertebrates and which appears well suited for encoding a graded receptor potential into a train of action potentials.
Corotto
F S
FS
Department of Physiology, University of Utah School of Medicine, Salt Lake City 84108, USA.
Piper
D R
DR
Chen
N
N
Michel
W C
WC
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D003035:Cobalt / Q000494:pharmacology; D004553:Electric Conductivity; D015640:Ion Channel Gating / Q000502:physiology*; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D015027:Zebrafish / Q000502:physiology*
D015220:Calcium Channels; D015221:Potassium Channels; D003035:Cobalt; D013779:Tetrodotoxin; D002118:Calcium