title: Effects of trifluoperazine and promethazine on the release of transmitter quanta at the mouse neuromuscular junction.
abstract: The present experiments examined the effects of phenothiazine derivatives, such as trifluoperazine and promethazine, on the release of transmitter quanta in preparations of the mouse diaphragm. The frequency (F, s-1) of miniature end-plate potentials and the quantal content (m) of endplate potentials were measured intracellularly at the same endplate in a bathing solution that contained 0.5-0.8 mM Ca2+ ions and 5 mM Mg2+ ions. Trifluoperazine (4 microM) significantly reduced both F and m. The inhibitory effect on m, but not on F, was subject to competition by Ca2+ ions. Promethazine at 48 microM, but not at 16 microM, reduced the quantal release. It was apparent that the effect of trifluoperazine was competitively antagonized by Ca2+ ions at motor nerve terminals.
authors.affiliation: Department of Pharmacology, University of Obihiro School of Veterinary Medicine, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nishimura
authors.forename: R
authors.initials: R
authors.lastname: Komatsu
authors.forename: Y
authors.initials: Y
authors.lastname: Taquahashi
authors.forename: Y
authors.initials: Y
authors.lastname: Shimizu
authors.forename: E
authors.initials: E
authors.lastname: Satoh
mesh_terms: D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D004594:Electrophysiology; D008297:Male; D051379:Mice; D009045:Motor Endplate / Q000502:physiology; D009469:Neuromuscular Junction / Q000378:metabolism* / Q000502:physiology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011398:Promethazine / Q000494:pharmacology*; D014268:Trifluoperazine / Q000494:pharmacology*
chemical_list: D018377:Neurotransmitter Agents; D014268:Trifluoperazine; D011398:Promethazine