Mechanisms of the non-neurotransmitter actions of acetylcholine in the neuromuscular apparatus.
Experiments on isolated phrenic-diaphragmatic preparations from rats showed that low acetylcholine concentrations increase the work capacity of exhausted muscle by increasing the level of evoked quantum transmitter release; acetylcholine also induced hyperpolarization of muscle fiber membranes. The effects of acetylcholine persisted for long periods of time. The modulating actions of acetylcholine are mediated by structures with different pharmacological characteristics from those of typical n- and m-cholinoreceptors; these mechanisms involved ouabain-sensitive isoforms of Na+,K+-ATPase and, perhaps, membrane K+ channels. The data obtained here support the possible existence of long-term neuronal regulation of the efficiency of neuromuscular transmission involving non-quantal acetylcholine, these mechanisms presumably developing differently in muscle fibers with different functional characteristics and abilities to adapt to physiological loading.
Krivoi
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A. A. Ukhtomskii Science Research Institute of Physiology, St. Petersburg State University, Russia.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D003964:Diaphragm / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004594:Electrophysiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009469:Neuromuscular Junction / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism; D010791:Phrenic Nerve / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D051381:Rats
D018377:Neurotransmitter Agents; D000109:Acetylcholine