title: [Preganglionic discharge induced by acetylcholine in the superior cervical ganglia of the rat].
abstract: ACh (5.10(-4) M), when applied to isolated ganglion preparations elicited an apparently antidromic discharge in the cervical sympathetic trunk. The intensity of this back-firing was found to be about 10 times lower than that of the postganglionic discharge evoked by ACh in the internal carotid nerve. Both responses however displayed a similar time course consisting mainly of an early and a late component. In the back-firing the early component died out in few seconds, while the late one lasted 20-30 seconds. The two components were cancelled by d-tubocurarine (5.10(-6) M) and atropine (10(-6) M) respectively, suggesting that both nicotinic and muscarinic cholinoceptive sites are involved. In chronically decentralized preparations ACh evoked a clear back-firing response not substantially different from that elicited in normal ganglia. Therefore it is likely that the back-firing phenomenon is not due to antidromic activation of preganglionic fibers. The back-firing observed in the rat superior cervical ganglion was interpreted as being due to activation of sympathetic neurons, known to give rise to recurrent axons in the cervical sympathetic cord.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004594:Electrophysiology; D005728:Ganglia, Sympathetic / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D001285:Atropine; D000109:Acetylcholine
vernacular_title: Scarica"pregangliare"indotta dall'acetilcolina nel ganglio cervicale superiore di ratto.