[Effects of 3,4-diaminopyridine on the contractions of guinea-pig tracheal smooth muscle induced by histamine and prostaglandin D2].
Effects of 3,4-diaminopyridine (DAP), which decreases the membrane K conductance, on the contractions of guinea-pig tracheal smooth muscle induced by histamine and prostaglandin D2 (PGD2) were investigated. Pretreatments with 5 X 10(-4) and 10(-3) M DAP increased the excitability of histamine-induced contraction. The increment of the excitability by DAP was not suppressed by tetrodotoxin (TTX), but by nifedipine (Nif). Pretreatment with 10(-3) M DAP did not affect the contraction induced by PGD2. The results suggest that DAP increases the excitability of histamine-induced contraction by activating the voltage-dependent Ca channels and that PGD2 contracts tracheal smooth muscle through a mechanism different from that of histamine.
Sonoki
H
H
Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Uchida
Y
Y
Tomaru
T
T
Sugimoto
T
T
D015761:4-Aminopyridine / Q000031:analogs & derivatives*; D000077770:Amifampridine; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D004357:Drug Synergism; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D015230:Prostaglandin D2; D011457:Prostaglandins D / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects* / Q000502:physiology
D000631:Aminopyridines; D011457:Prostaglandins D; D013779:Tetrodotoxin; D006632:Histamine; D015761:4-Aminopyridine; D009543:Nifedipine; D000077770:Amifampridine; D015230:Prostaglandin D2