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Combined voltage‐clamp and dialysis of Myxicola axons: behaviour of membrane asymmetry currents.
Author(s) -
Bullock J O,
Schauf C L
Publication year - 1978
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1978.sp012306
Subject(s) - chemistry , time constant , voltage clamp , axon , biophysics , sodium channel , asymmetry , sodium , membrane potential , nuclear magnetic resonance , physics , anatomy , biology , biochemistry , organic chemistry , quantum mechanics , electrical engineering , engineering
4. A new technique for the simultaneous internal dialysis and voltage‐clamp of Myxicola axons is described and shown to control the internal composition of the axon adequately. 2. The permeability ratio (PNa/PK) of the sodium channel is 15.5 in axons dialysed with sodium‐free solutions, somewhat higher than observed in perfused axons. 3. Asymmetry currents are easily recorded in dialysed Myxicola axons. At 4‐‐5 degrees C for pulse durations sufficiently short Qon = Qoff with a maximum charge displacement of 10 nC/cm2 and half the charge being displaced by a step to ‐32 mV. Maximum slope of the Q(V) curve is 15 mV/e‐fold change in charge displaced. The time constant tau on reaches a maximum of 325 microseconds at a potential of ‐23 mV. 4. The time course of sodium activation cannot be adequately accounted for by (Q/Q infinity) X using any single value of X for potentials between ‐40 and 40 MV. 5. Both asymmetry currents and INa are inactivated by the same amount when Myxicola axons are repetitively depolarized at frequencies from 0.1 to 50 Hz.