Effects of histamine on the resting and stimulation-induced release of [3H]-noradrenaline in guinea-pig isolated atria.
1 The sympathetic transmitter stores of guinea-pig isolated atria were labelled with [3H]-noradrenaline. The effects of histamine (0.3 to 100 mumol/l) on resting and stimulation-induced (S-I, 2 Hz for 10 s) release of radioactivity were investigated. 2 Histamine, in low concentrations (0.3 and 1 mumol/l) had no effect on resting release but inhibited S-I release of radioactivity. The inhibition was abolished by the H2-receptor antagonist, cimetidine (10 mumol/l) and also by the H1-receptor antagonist, mepyramine (1 mumol/l). 3 The inhibitory actions of histamine on S-I release were not due to indirect effects involving alpha-adrenoceptors, beta-adrenoceptors, muscarinic cholinoceptors or prostaglandin synthesis. 4 Histamine in a high concentration (100 mumol/l) increased the resting and S-I release of radioactivity. The increase in resting release was abolished by the neuronal uptake blocking drug cocaine (30 mumol/l) but the increase in S-I release was only partially blocked by cocaine.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002927:Cimetidine / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D006168:Guinea Pigs; D006325:Heart Atria / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology
D001285:Atropine; D002927:Cimetidine; D006632:Histamine; D011433:Propranolol; D011738:Pyrilamine; D003042:Cocaine; D009638:Norepinephrine; D007213:Indomethacin; D010646:Phentolamine