KINETICS OF ACTIVATION OF THE SODIUM CONDUCTANCE IN THE SQUID GIANT-AXON
KINETICS OF ACTIVATION OF THE SODIUM CONDUCTANCE IN THE SQUID GIANT-AXON
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DOI：
10.1113/jphysiol.1983.sp014601
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发表时间：
1983-01-01
影响因子：
5.5
通讯作者：
KIMURA, JE
中科院分区：
文献类型：
--
作者：
KEYNES, RD;KIMURA, JE
The time course of the rise in Na conductance during positive voltage-clamp pulses was measured in squid giant axons perfused with CsF and immersed in low Na solutions. The initial transients were eliminated by subtraction of records made after blocking the Na-channels with tetrodotoxin. The value of .tau.m as defined by Hodgkin .apprx. Huxley (1952) passed through a well defined maximum at a membrane potential of .apprx. -35 mV. On fitting the initial inflexion in the rise of INa to the expression MXh instead of m3h, the value of X varied from axon to axon between 2.9-4.4, with an average of 3.5. For any given axon, X did not vary significantly with pulse potential. Measurements of Tm were made on approaching each value of the membrane potential from the negative and from the positive side. The cube law kinetics of the Hodgkin-Huxley equations were closely obeyed. Application of a negative prepulse to -180 mV delayed the rise of conductance by 20 .mu.s at 7.degree. C without obviously changing .tau.m. Comparisons of the voltage dependence of .tau.m with that of the time constant .tau.1 of the fast relaxation of the asymmetry current measured in the same axon, showed that .tau.1 was smaller than .tau.m except at positive potentials, was less steeply voltage-dependent and reached its maximum at a more positive potential.
