The effect of morphine on human neuromuscular transmission.
By utilizing high frequency nerve stimulation, we observed the effects of morphine sulphate, 0.5 mg.kg-1 on human neuromuscular transmission. Tetanic fade at 50, 100 and 200 hz did not change during the one hour period after infusion of morphine. Post-tetanic depression (PTD) of single twitch response increased progressively with time over the one-hour study period. This was most marked with the 100 and 200 hz tetanic frequencies. In contrast, control subjects displayed either no change, or a slight increase (post-tetanic facilitation; PTF), over a similar one-hour test period. We believe these results are best explained by a presynaptic action of morphine, whereby intraterminal mobilization of acetylcholine is impaired by the opiate narcotic drug.
D000109:Acetylcholine / Q000378:metabolism; D000328:Adult; D004558:Electric Stimulation; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects*; D014459:Ulnar Nerve / Q000502:physiology
D009020:Morphine; D000109:Acetylcholine