[Analysis of postsynaptic currents in the phasic and tonic muscle fibers of the extraocular muscles of the rat].
The miniature end-plate currents (MEPCs), miniature postjunctional currents (MPJCs) and mean values of life-time of open ionic channels (tau chan) were compared in experiments on fast and tonic muscle fibres. The rise-time and decay-time constants of MPJCs in tonic fibres were 2.5 and 4-5 times (respectively) longer than those of MEPCs in fast fibres; tau chan in tonic synapses was 2.2 times higher than in fast ones. Inhibition of AChE induced more pronounced prolongation of MEPCs (4.4 times) than MPJCs (1.8 times). As a result, the difference between the time decay of MPJCs and MEPCs reduced to 1.6 times. Thus, a more prolonged decay of MPJCs in tonic fibres in comparison with MEPCs in fast fibres was due to a larger value of tau chan and lower activity of AChE, that favours repetitive interaction between ACh-molecules and choline receptors causing prolongation of the decay of the synaptic response. The time course of MEPCs and tau chan in skeletal slow-twitch muscle fibres was significantly shorter than those in extraocular tonic muscle fibres.
D000110:Acetylcholinesterase / Q000502:physiology*; D000818:Animals; D007473:Ion Channels / Q000502:physiology; D008564:Membrane Potentials; D009045:Motor Endplate / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology*; D009801:Oculomotor Muscles / Q000166:cytology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D009435:Synaptic Transmission
D007473:Ion Channels; D000110:Acetylcholinesterase
Analiz postsinapticheskikh tokov v faznykh i tonicheskikh myshechnykh voloknakh vneshneĭ glaznoĭ myshtsy krysy.