title: Interaction of verapamil with d-tubocurarine and cholinergic agonists at the avian neuromuscular junction.
abstract: The effect of verapamil on neuromuscular transmission and muscle contraction was studied in the skeletal muscle of chick in vitro. The interactions of verapamil with d-tubocurarine (d-TC)-induced neuromuscular blockade, acetylcholine (ACh) and tetraethylammonium (TEA)-induced contractures were also studied. The purpose of the present investigation was to see if verapamil: intensified the neuromuscular blockade produced by d-TC; modified the cholinergic responses to ACh, TEA; and inhibited both directly and indirectly elicited twitch contractions. The results showed that verapamil (1-100 micrograms/ml, 2-200 mumol/l) had a neuromuscular blocking activity on its own; i.e. it reduced both directly and indirectly evoked twitch contractions, and intensified the neuromuscular blockade produced by d-TC. In addition, verapamil reduced the contractures produced by ACh and TEA in the chick muscle. The results are in favour of the possibility that verapamil acts by a mixture of pre- and post-junctional effects at the chick neuromuscular junction.
mesh_terms: D000109:Acetylcholine / Q000008:administration & dosage*; D000818:Animals; D002645:Chickens; D004347:Drug Interactions; D066298:In Vitro Techniques; D009469:Neuromuscular Junction / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000008:administration & dosage*; D014403:Tubocurarine / Q000008:administration & dosage*; D014700:Verapamil / Q000008:administration & dosage*
chemical_list: D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D014700:Verapamil; D000109:Acetylcholine; D014403:Tubocurarine