PHENTHONIUM INDUCES A TRANSIENT INCREASE OF ACETYLCHOLINE EFFLUX FROM MOTOR-NERVE TERMINALS

PHENTHONIUM INDUCES A TRANSIENT INCREASE OF ACETYLCHOLINE EFFLUX FROM MOTOR-NERVE TERMINALS

Author Cysneiros, Roberta Monterazzo Autor UNIFESP Google Scholar
Lima-Landman, Maria Teresa Riggio de Autor UNIFESP Google Scholar
Souccar, Caden Autor UNIFESP Google Scholar
Lapa, Antonio José Autor UNIFESP Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Abstract Phenthonium (10-50-mu-M), a quaternary derivative of 1-hyoscyamine, increases the frequency of miniature end-plate potentials (2-5 fold) and blocks the nicotinic receptor-ionic channel in skeletal muscles. When tested on rat diaphragms previously incubated with [H-3]choline, phenthonium (50-mu-M) increased the spontaneous release of radiolabelled acetylcholine (ACh) from 11.6 +/- 6.4 to 110.5 +/- 40.2 x 10(3) dpm/g within 15 min. The effect was transient, declining to 24.6 +/- 14.7 after 50 min. Subsequent electrical stimulation still in the presence of phenthonium increased the efflux to 164.7 +/- 45.3. The fractional release relative to the level before stimulation did not differ from controls. Phenthonium (20-mu-M) did not increase the spontaneous ACh release but doubled the efflux induced by nerve stimulation. The present results, compared to previous electrophysiological findings, indicate that quantal and nonquantal release are increased by phenthonium. They also show that the transient effect is not due to ACh depletion in nerve terminals.
Keywords CHOLINERGIC MODULATION
MOTOR NERVE TERMINAL
ACETYLCHOLINE EFFLUX
Language English
Date 1991-01-01
Published in Brazilian Journal Of Medical And Biological Research. Sao Paulo: Assoc Bras Divulg Cientifica, v. 24, n. 10, p. 1055-1058, 1991.
ISSN 0100-879X (Sherpa/Romeo, impact factor)
Publisher Assoc Bras Divulg Cientifica
Extent 1055-1058
Access rights Closed access
Type Article
Web of Science ID WOS:A1991GR20300011
URI http://repositorio.unifesp.br/11600/42997

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