Histamine-operated calcium channels in intestinal smooth muscle of the guinea-pig.
The effects of Bay K 8644 and of nifedipine on histamine-induced mechanical and electrical responses were studied in the longitudinal smooth muscle of the ileum and in the taenia coli isolated from the guinea-pig. Nifedipine (10(-9)-10(-7) M) depressed the tonic and phasic components of histamine contraction. Phasic tension was less sensitive to nifedipine inhibition than was tonic tension (I50: 27 +/- 6 and 2.6 +/- 0.4 nM respectively). Bay K 8644 (10(-8)-10(-7) M) increased tension and rhythmic activity of intestinal smooth muscle and potentiated the histamine responses. The phasic tension evoked by histamine 10(-5) M and the phasic tension evoked by the KCl depolarizing solution showed the same sensitivity to nifedipine inhibition (I50: 28 +/- 5 nM) and were similarly potentiated by Bay K 8644. The tonic tension in response to the KCl-depolarizing solution was more sensitive to nifedipine inhibition than was the tonic tension in response to histamine and was not potentiated by Bay K 8644. These results indicate that different Ca entry pathways, dependent or not on modification of the membrane potential, are involved in the contractile response evoked by histamine in intestinal smooth muscle.
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D004594:Electrophysiology; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D007473:Ion Channels / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology
D007473:Ion Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D006632:Histamine; D009543:Nifedipine