New evidence for a presynaptic action of prednisolone at neuromuscular junctions |
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Authors: | Dal Belo Cháriston André Leite Gildo Bernardo Fontana Marcos Dias Corrado Alexandre Pinto Zanandréa Baso Ana Cristina Moreno Serra Carmen Sílvia Oliveira Antonio Carlos Rodrigues-Simioni Léa |
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Institution: | Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), P.O. Box 6111, CEP 13083-970, Campinas, SP, Brazil. |
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Abstract: | The action of prednisolone at the neuromuscular junction was studied in mouse isolated phrenic nerve-diaphragm and rat external popliteal/sciatic nerve-tibialis anterior muscle preparations. Prednisolone (0.03 mM and 0.3 mM) did not alter the twitch-tension in phrenic nerve-diaphragm preparations after 120 min, but increased the frequency (170 +/- 4%) and amplitude (200 +/- 13%) of miniature end-plate potentials. Quantal content was not influenced by the glucocorticoid treatment. Prednisolone (400 microg/kg) did not change the twitch-tension in rat external popliteal/sciatic nerve-tibialis anterior muscle preparations. However, this steroid (0.3 mM) prevented the neuromuscular blockade by d-tubocurarine (1.45 microM) in mouse preparations by 70 +/- 10% (P < 0.05). A similar effect (82 +/- 6% protection, P < 0.05) occurred in rats treated with prednisolone (400 microg/kg) before d-tubocurarine (225 microg/kg). In phrenic nerve-diaphragm preparations, prednisolone (0.3 mM) increased (13 +/- 4%, p < 0.05) the twitch-tension in the presence of beta-bungarotoxin (1 microM), and prevented the blockade produced by this toxin (0.15 microM) in its third phase of action. This presynaptic facilitatory effect may contribute to the usefulness of prednisolone in myasthenia gravis. |
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Keywords: | electrophysiology facilitatory effect myasthenia gravis neuromuscular junction prednisolone |
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