[Effect of the quantal composition, membrane potential and cholinoreceptor density on the temporal flow of the end plate current in the rat under conditions of acetylcholinesterase inhibition].
The factors determining the decay of multiquantal end plate currents (EPC) were studied in the diaphragm muscle of rat by the comparison of EPC and miniature EPC (MEPC) amplitude--temporal characteristics. The decay of EPC (quantal content 25-100) was 1.2 times slower than the decay of MEPC when AChE was active. The AChE inhibition by armine or neostigmine made this difference 10-100 times higher. In most synapses the decay of multiquantal EPC can be approximated by a sum of two or three exponents. It depended on the quantal content and 3-exponential EPC could be transformed in 2-exponential and later to monoexponential ones if increasing concentration of magnesium ions. A slow component of EPCs (but not of MEPC) decay was highly sensitive to concentration of magnesium ions and had 3 times higher dependence of the membrane potential value than that one of MEPC. The irreversible blocking of receptors by alpha-bungarotoxin (alpha-BuTX) accelerated the decay of MEPC but the decay of multiquantal EPC changed in two phases: it was prolonged at the beginning of alpha-BuTX action followed by its acceleration, but never the time of the decay of EPC had achieved the apparent open time of ACh-activated ionic channels. It is suggested that during the multiquantal EPC generation not only the synchronization of opening but the kinetic of ACh-activated channels is changed, probably by blocking of this channels by high concentrations of endogenous ACh.
Giniatullin
R A
RA
Shvetsov
A B
AB
D000818:Animals; D001138:Armin / Q000494:pharmacology; D002038:Bungarotoxins / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009045:Motor Endplate / Q000187:drug effects / Q000502:physiology*; D009388:Neostigmine / Q000494:pharmacology; D011789:Quantum Theory; D051381:Rats; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D002038:Bungarotoxins; D002800:Cholinesterase Inhibitors; D011950:Receptors, Cholinergic; D009388:Neostigmine; D001138:Armin; D008274:Magnesium
Vliianie kvantovogo sostava, membrannogo potentsiala i plotnosti kholinoretseptorov na vremennoe techenie tokov kontsevoĭ plastinki krysy v usloviiakh ingibirovaniia atsetilkholinésterazy.