Dynamics of aminopyridine block of potassium channels in squid axon membrane

J. Z. Yeh, G. S. Oxford, C. H. Wu, T. Narahashi

Research output: Contribution to journalArticle

208 Citations (Scopus)

Abstract

Aminopyridines (2 AP, 3 AP, and 4 AP) selectively block K channels of squid axon membranes in a manner dependent upon the membrane potential and the duration and frequency of voltage clamp pulses. They are effective when applied to either the internal or the external membrane surface. The steady state block of K channels by aminopyridines is more complete for low depolarizations, and is gradually relieved at higher depolarizations. The K current in the presence of aminopyridines rises more slowly than in control, the change being more conspicuous in 3 AP and 4 AP than in 2 AP. Repetitive pulsing relieves the block in a manner dependent upon the duration and interval of pulses. The recovery from block during a given test pulse is enhanced by increasing the duration of a conditioning depolarizing prepulse. The time constant for this recovery is in the range of 10-20 ms in 3 AP and 4 AP, and shorter in 2 AP. Twin pulse experiments with variable pulse intervals have revealed that the time course for re establishment of block is much slower in 3 AP and 4 AP than in 2 AP. These results suggest that 2 AP interacts with the K channel more rapidly than 3 AP and 4 AP. The more rapid interaction of 2 AP with K channels is reflected in the kinetics of K current which is faster than that observed in 3 AP or 4 AP, and in the pattern of frequency dependent block which is different from that in 3 AP or 4 AP. The experimental observations are not satisfactorily described by alterations of Hodgkin Huxley n type gating units. Rather, the data are consistent with a simple binding scheme incorporating no changes in gating kinetics which conceives of aminopyridine molecules binding to closed K channels and being released from open channels in a voltage dependent manner.

Original languageEnglish (US)
Pages (from-to)519-535
Number of pages17
JournalJournal of General Physiology
Volume68
Issue number5
StatePublished - 1976
Externally publishedYes

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Aminopyridines
Decapodiformes
Potassium Channels
Axons
Membranes
Membrane Potentials

ASJC Scopus subject areas

  • Physiology

Cite this

Yeh, J. Z., Oxford, G. S., Wu, C. H., & Narahashi, T. (1976). Dynamics of aminopyridine block of potassium channels in squid axon membrane. Journal of General Physiology, 68(5), 519-535.

Dynamics of aminopyridine block of potassium channels in squid axon membrane. / Yeh, J. Z.; Oxford, G. S.; Wu, C. H.; Narahashi, T.

In: Journal of General Physiology, Vol. 68, No. 5, 1976, p. 519-535.

Research output: Contribution to journalArticle

Yeh, JZ, Oxford, GS, Wu, CH & Narahashi, T 1976, 'Dynamics of aminopyridine block of potassium channels in squid axon membrane', Journal of General Physiology, vol. 68, no. 5, pp. 519-535.
Yeh, J. Z. ; Oxford, G. S. ; Wu, C. H. ; Narahashi, T. / Dynamics of aminopyridine block of potassium channels in squid axon membrane. In: Journal of General Physiology. 1976 ; Vol. 68, No. 5. pp. 519-535.
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