title: Glucocorticoid-induced changes in synaptic vesicles of rat phrenic nerve terminals.
abstract: The mean cross sectional area of synaptic vesicle profiles of the myoneural junction of rat diaphragm is increased significantly when rats are injected i.p. with single doses of 200 micrograms/kg dexamethasone 1/2 hr to 8 hr previously to a control injection of 0.9% NaCl. A maximum effect is observed at 8 hr after pretreatment with dexamethasone. The treatment of rats with hemicholinium-3 (300 micrograms/kg) induces a significant reduction of the vesicle size. Complete prevention of this decrease in vesicle size is already observed when the animals are pretreated with a single dose of 200 micrograms/kg dexamethasone 1/2 hr before treatment with 300 micrograms/kg hemicholinium-3. Dexamethasone in the same dose causes an optimum increase of the mean cross sectional area when it is given 1 hr before treatment of the animals with hemicholinium-3. It is concluded that glucocorticoids have direct actions in both "normal" motor nerve terminals and in motor nerve terminals with a deficient choline transport system, which may contribute to their proposed beneficial effects in certain cases of muscle weakness.
mesh_terms: D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology; D003964:Diaphragm / Q000187:drug effects; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology*; D006426:Hemicholinium 3 / Q000494:pharmacology; D009411:Nerve Endings / Q000187:drug effects*; D009469:Neuromuscular Junction / Q000187:drug effects; D010791:Phrenic Nerve / Q000187:drug effects; D051381:Rats; D009435:Synaptic Transmission / Q000187:drug effects; D013572:Synaptic Vesicles / Q000187:drug effects*
chemical_list: D005938:Glucocorticoids; D006426:Hemicholinium 3; D003907:Dexamethasone