title: Electrically induced release of radiolabeled histamine from rat hippocampal slices: opposing roles for H1- and H2-receptors.
abstract: Rat hippocampal slices were preloaded with 3H-histamine and superfused with physiological medium and electrically stimulated in the absence (S1) and in the presence (S2) of drugs. The electrically evoked 3H-overflow consisted mainly of histamine, was Ca++ dependent and completely blocked by tetrodotoxin, all pointing towards an impulse triggered neuronal release. Mepyramine, promethazine and diphenhydramine the H1-antagonists, inhibited the stimulation evoked histamine release in a dose dependent manner. Burimamide and cimetidine, the H2-antagonists, enhanced the stimulation induced release of histamine whereas dimaprit, the H2-antagonist, had the opposite effect. Histamine by itself did not influence its own release. The observations indicate an opposing role for H1- and H2-receptors in modulating spike induced histamine release and represents a functional consequence of the stimulation of the receptors.
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D006624:Hippocampus / Q000378:metabolism*; D006636:Histamine Release; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011968:Receptors, Histamine / Q000502:physiology*; D011969:Receptors, Histamine H1 / Q000502:physiology*; D011970:Receptors, Histamine H2 / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014316:Tritium
chemical_list: D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D014316:Tritium; D013779:Tetrodotoxin