Electromagnetic stimulation and inhibition of nerve conduction in frog isolated sciatic nerve-gastrocnemius muscle preparation.
The effect of electromagnetic stimulation on nerve conduction and on muscle contraction was studied in isolated frog sciatic nerve-gastrocnemius muscle preparation. The nerve trunk was passed through an induction copper coil and current was induced from a d.c. source 1.5-4 V at a frequency of 100 min-1, for 20-120 s duration, via an operating switch. Normal indirectly-elicited twitch (0.5 Hz with 0.6 V, supramaximal, and 1 ms pulse duration) tension was elicited, repetitively, and this was interrupted by magnetic induction. Inhibition of the twitch tension was taken as a measure of conduction block. The results showed that magnetic stimulation inhibited or blocked the twitch contractions (control 3.2 +/- 0.1 g, tension, mean +/- s.e., n = 8), in 4-5 min, and hence it blocked nerve conduction in this preparation. Recovery was achieved within 4-5 min, after washing out the preparation in Ringer solution. The mechanism of inhibition was interpreted in terms of an interference with ionic fluxes across the cell membrane. A comparison of electrical and magnetic stimulation was made and this was related to their clinical and experimental implications.
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Anaesthetics Unit, London Hospital Medical College, Whitechapel, U.K.
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D000818:Animals; D001001:Anura; D055590:Electromagnetic Phenomena / Q000295:instrumentation*; D066298:In Vitro Techniques; D009119:Muscle Contraction; D009431:Neural Conduction; D009469:Neuromuscular Junction / Q000502:physiology*; D012584:Sciatic Nerve / Q000502:physiology