Voltage-clamp analysis of the voltage-gated sodium current of the rat pituitary melanotroph.
By using the whole-cell recording technique the Na+ current in cultured melanotrophs of the adult rat pituitary was studied. The Na+ current was eliminated by 1 microM TTX and its equilibrium potential confirmed that it was carried predominantly by Na+. The activation threshold was near -40 mV and half-maximal activation occurred at approximately -23 mV. The peak amplitude of 640 +/- 110 pA (n = 8) occurred near -10 mV. Steady-state half-inactivation occurred near -50 mV. Recovery from inactivation at -70 mV was biexponential: approximately half of the channels recovered with a time constant of 13 ms whereas the slower phase of recovery had a time constant of 430 ms. These properties of the Na+ current are discussed in relation to its role in cell firing and hormone secretion.
Department of Physiology, University of British Columbia, Vancouver, Canada.
S J
SJ
Kehl
D000818:Animals; D002478:Cells, Cultured; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D015222:Sodium Channels; D013779:Tetrodotoxin