title: Comparison of the effects of calcium and the calcium channel stimulant Bay k 8644 on neomycin-induced neuromuscular blockade.
abstract: The effects of calcium and the calcium channel stimulant Bay k 8644 on neomycin-induced neuromuscular blockade were evaluated using rat phrenic nerve-hemidiaphragm preparations in vitro. neomycin showed maximum potency in inducing neuromuscular blockade when the calcium concentration in the bath was 1 mM. Higher calcium concentrations (1.5, 2 and 4 mM) produced a gradual decrease in neomycin potency, manifested as a progressive shift to the right of neomycin concentration-response curves. Bay k 8644 (0.1 and 1 microM) did not significantly modify indirectly elicited diaphragm contractions per se, nor did it antagonize neomycin-induced neuromuscular blockade. A higher concentration of Bay k 8644 (10 microM) antagonized indirectly elicited contractions. In conclusion, our results show that Bay k 8644, at concentrations causing calcium channel stimulation at the cardiac and vascular level, did not exert stimulant effects in a nerve-skeletal muscle preparation, suggesting that its action may be tissue-selective to a certain degree.
authors: Department of Pharmacology, University of Granada, Medical School, Spain.
authors: J M
authors: JM
authors: Baeyens
authors: E
authors: E
authors: Del Pozo
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D003964:Diaphragm / Q000187:drug effects; D005260:Female; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009355:Neomycin / Q000494:pharmacology*; D009466:Neuromuscular Blocking Agents; D009469:Neuromuscular Junction / Q000187:drug effects; D010791:Phrenic Nerve / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D015220:Calcium Channels; D009466:Neuromuscular Blocking Agents; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009355:Neomycin; D002118:Calcium