Novel effects of guanidine on the neuromuscular junction
| Autor: | J. Prado-Franceschi, N.F. Heluany, Léa Rodrigues-Simioni, Maria Alice da Cruz-Höfling, A.P. Corrado, G. Ballejo, Gildo Bernardo Leite, I. Silva-Carvalho |
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| Rok vydání: | 1997 |
| Předmět: |
Male
Cromakalim Potassium Channels Neuromuscular Junction Neuromuscular transmission Motor nerve In Vitro Techniques Pharmacology Guanidines Neuromuscular junction Mice chemistry.chemical_compound medicine Animals Benzopyrans Pyrroles 4-Aminopyridine Guanidine Neuromuscular Blockade Electromyography Evoked Potentials Motor Electric Stimulation medicine.anatomical_structure chemistry Anesthesia Tetrodotoxin Calcium Chickens Muscle Contraction medicine.drug |
| Zdroj: | General Pharmacology: The Vascular System. 28:599-605 |
| ISSN: | 0306-3623 |
| DOI: | 10.1016/s0306-3623(96)00229-7 |
| Popis: | 1. The effects of guanidine on the isolated mouse phrenic nerve diaphragm (MPND) and chick biventer cervicis (CBC) neuromuscular preparations were determined by myographic and electrophysiological methods. 2. Guanidine at concentrations of 5-10 mM induced an initial facilitation followed by neuromuscular blockade in both preparations. In the isolated MPND such blockade was associated with the abolition of miniature end-plate potentials (MEPPs), but in the CBC the acetylcholine-induced contracture remained unimpaired. After guanidine removal, a heretofore undescribed pronounced facilitation of neuromuscular transmission associated with an increase in MEPP frequency was observed. Simultaneously, the muscular contractions exhibited delayed relaxation and aftercontractions. 3. The K+ channel opener, cromakalim (100-200 microM) inhibited both the well-described initial and the novel postremoval facilitatory effects of guanidine in a concentration-dependent manner. These findings are consistent with the proposal that guanidine blocks K+ channels in motor nerve endings. 4. The guanidine-induced NMB was reverted by increasing the Ca2+ concentration (1.8-5 mM) in the nutritive solution. 5. Tetrodotoxin (TTX, 1.56 microM) did not influence the increase in MEPPS frequency induced by guanidine (10 mM) but did reduce the rise in MEPPS frequency observed after guanidine removal. 6. The present findings indicate that the effects of guanidine on the neuromuscular junction are more complex than currently described because they include a neuromuscular blockade and a post-removal facilitation previously unreported in the literature. |
| Databáze: | OpenAIRE |
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