A Varicosity Ensemble Model of Sympathetic Neuromuscular Transmission
Varicosities within sympathetic nerve terminals appear to differ widely in function, e.g., in secretory responsiveness to action potentials.1 By recording excitatory junction currents (EJCs) at visualised nerve terminals in mouse vas deferens, the probability of release of a quantum of ATP from single varicosities (p ATP ) was found to be highly nonuniform, in a few 0.1–0.5 but in most 0.01 or less.2 ATP-mediated responses to nerve impulse trains may thus be evoked by repeated release of ATP quanta from ‘strong’ varicosities while weak’ varicosities remain ‘silent’ (hotspot transmission). The question is if this applies as well to transmission mediated by co-released noradrenaline (NA).3
KeywordsCarbon Fibre Sympathetic Nerve Terminal Neuronal Reuptake Sympathetic Nerve Release Secretory Responsiveness
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- 15.A.R. Martin, Junctional transmission II. Presynaptic mechanisms. In Handbook of Physiology, pp. 329–355 (1977).Google Scholar