| Title | Non-quantal release of acetylcholine from parasympathetic nerve terminals in the right atrium of rat. | | Author(s) | Abramochkin DV, Nurullin LF, Borodinova AA, Tarasova NV, Sukhova GS, Nikolsky EE, Rosenshtraukh LV | | Institution | 1 Moscow State University of M.V.Lomonosov; | | Source | Exp Physiol 2009 Sep 18. | | Abstract | Acetylcholinesterase (AChE) inhibitors provoke typical cholinergic effects in the isolated right atrium of rat due to the accumulation of acetylcholine (ACh). Our study was designed to show that in the absence of vagal impulse activity ACh is released from the parasympathetic nerve fibers by means of non-quantal secretion generally. The conventional microelectrode technique was used to study changes in action potential (AP) configuration in the right atrium preparation of rat during application of AChE inhibitors. Staining with lipophilic fluorescent dye FM1-43 was used to demonstrate presence of endocytosis in cholinergic endings. AChE inhibitors armin (10-7-10-5M) and neostigmine (10-7-5.10-6M) caused reduction of AP duration and cycle length prolongation. These effects were abolished by atropine, and therefore are mediated by ACh, accumulated in the myocardium during AChE inhibition. Putative block of postganglionic neurons impulse activity by tetrodotoxin (5.10-7M) and blocker of ganglionic transmission hexomethonium (2.10-4M) as well as the block of all forms of quantal release with (Clostridium) botulinum type A toxin (50 U/ml) didn't alter effects of armin. Experiments with FM1-43 dye confirmed the effective block of exocytosis by botulinum toxin. Selective inhibition of choline uptake system using hemicholinium III (10-5M), which blocks non-quantal release in the neuromuscular junction, suppressed effects of AChE inhibitors. Thus, accumulation of ACh is likely to be caused by non-quantal release from cholinergic terminals. We suppose that non-quantal release of ACh shown earlier in the neuromuscular junction, is present in cholinergic postganglionic fibers of the rat heart in addition to quantal release. | | Language | ENG | | Pub Type(s) | JOURNAL ARTICLE
| | PubMed ID | 19767403 |
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