[Mechanism of paradoxical resistance of the digastric muscle to the action of tetanus toxin].
Excitability parameters of m. masseter and m. digastricus fibers (resting minute potential--MP, action potential--AP, critical level of depolarization--CLD and rheobase currents) were determined in anesthetized rats (nembutal, 40 mg/kg) on days 3-4 and 10-15 after local intramuscular tetanus toxin injection (20 and 40 mouse Dlm, respectively). The development of local tetanus in m. masseter was characterized by typical excitability changes--a decrease in MP and AP. Local spasm in m. digastricus under analogous conditions of tetanus toxin injection was absent, while excitability tests demonstrated MP, AP and CLD augmentation. As m. digastricus motoneurons are devoid of inhibitory synaptic regions, these nervous cells are not affected by tetanus toxin.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D008297:Male; D008410:Masticatory Muscles / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009132:Muscles / Q000187:drug effects*; D009334:Neck Muscles / Q000187:drug effects*; D051381:Rats; D013744:Tetanus Toxin / Q000494:pharmacology*; D014313:Trismus / Q000139:chemically induced
D013744:Tetanus Toxin
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