Summary
The effects on neuromuscular transmission of DMAE, an analog of hemicholinium-3, were studied using frog isolated sartorius muscles. DMAE (1 to 10 μM) had no effect on the resting membrane potential or on membrane resistance. Depolarization produced by nicotine was blocked by 10 μM DMAE but not by lower concentrations. The amplitude of EPP's, but not that of the mepp's, was increased by DMAE. The amplitudes of EPP's evoked by trains of stimulation at rates of 5 or 10/sec were not sustained after treatment of the muscles with DMAE. Quantal content but not quantal size was reduced during the fade of the EPP's. The fade-inducing property of DMAE dependend on the Mg++/Ca++ of the bathing solution. Situations favoring high quantal content increased the responsiveness of the junction to DMAE. It was concluded that DMAE acted on the prejunctional terminals to modify transmitter release, probably by interfering with the mobilization of transmitter.
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This research was supported by grant NS-07540-6, Institute of Neurological Diseases and Stroke, N.I.H., U.S.P.H.S.
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Volle, R.L. Frequency dependent decrease of quantal content in a drug-treated neuromuscular junction. Naunyn-Schmiedeberg's Arch. Pharmacol. 278, 271–284 (1973). https://doi.org/10.1007/BF00500288
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DOI: https://doi.org/10.1007/BF00500288