Tetraethylammonium-methohexitone induced contractures and miniature end-plate potential discharge in the chick biventer cervicis muscle.
End-plate and miniature end-plate potentials (EPP, MEPP) were recorded in the chick biventer cervicis muscle in vitro. The control frequency of discharge of MEPPs was 5.97 +/- 1.04 min-1, n = 10. Methohexitone (8.8 X 10(-5) M) did not affect the frequency of MEPP discharge, but tetraethylammonium (TEA, 2.4-9.5 mM), reduced the frequency to 32.9 +/- 8.6% of the control. In the presence of neostigmine (3.3 X 10(-6) M) methohexitone (8.8 X 10(-5) M) reduced MEPP frequency to 38.7 +/- 5.4% of the control and TEA (2.4-9.5 mM) further reduced the frequency to 8.7 +/- 2.1% of the control. After a transient facilitation of the EPP, TEA (2.4-9.5 mM) in the presence of methohexitone (8.8 X 10(-5) M) and neostigmine (3.3 X 10(-6) M) markedly reduced EPP amplitude. The contractures which TEA produced in the presence of methohexitone were not due to an increase in the spontaneous release of vesicular ACh.
D000818:Animals; D002645:Chickens; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008723:Methohexital / Q000494:pharmacology*; D009045:Motor Endplate / Q000187:drug effects*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009388:Neostigmine / Q000494:pharmacology; D009469:Neuromuscular Junction / Q000187:drug effects*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*
D013757:Tetraethylammonium Compounds; D009388:Neostigmine; D008723:Methohexital