The flickery block of ATP-dependent potassium channels of skeletal muscle by internal 4-aminopyridine

✍ Scribed by N. W. Davies; A. I. Pettit; R. Agarwal; N. B. Standen

• Book ID: 104746832
• Publisher: Springer
• Year: 1991
• Tongue: English
• Weight: 653 KB
• Volume: 419
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00373743

✦ Synopsis

We have examined the effects of 4-aminopyridine (4-AP) on single ATP-dependent potassium channels in patches excised from frog skeletal muscle. 4-AP applied to the internal face of the membrane caused a flickery block. We could not detect any flickery block when 10 mM 4-AP was applied to the external surface of the membrane. The reduction in mean unitary current by internal 4-AP was consistent with 1 : 1 binding with a K d of 3.3 mM at 0 mV. The block was voltage-dependent, increasing with depolarization with an effective valency of 0.57. Rate constants for blocking and unblocking by 4-AP were obtained by fitting//functions to the distribution of current amplitudes. Both rate constants were voltage-dependent. At 0mV they were 17mM -1 ms -1 and 61 ms -1. Simulation of the block using these rate constants produced a flickery block very similar to that observed experimentally.