title: Different mechanisms are responsible for the contractile effects of histaminergic compounds on isolated intestinal smooth muscle cells.
abstract: The effects of histamine and dimaprit on intestinal smooth muscle contractility were investigated on isolated cells from longitudinal muscle of the guinea pig ileum. Both histamine (10(-14)-10(-10) M) and dimaprit (10(-13)-10(-10) M) exerted a concentration-dependent contraction of intestinal cells, causing a maximum decrease in cell length of about 20%. This effect was not significantly different from that induced by cholecystokinin-octapeptide (CCK-8) 10(-9) M. The concentration-response curves to histamine and dimaprit were shifted to the left in the presence of the histamine H2-receptor antagonist famotidine (10(-7) M) indicating the occurrence in the smooth muscle of H2 receptors mediating relaxation. Whereas the contraction produced by histamine was competitively antagonized by the H1 receptor antagonist mepyramine (10(-8) M), neither mepyramine (10(-7) M) nor temelastine (10(-7) M) did modify the contractile effect of dimaprit. In contrast, atropine (10(-8) M) significantly depressed the maximum response to dimaprit without affecting that exerted by histamine. These data indicate that histamine and dimaprit can modify intestinal contractility, by acting via different mechanisms; while the contractile action of histamine is related to H1 receptor activation, that produced by dimaprit involves cholinergic pathways.
authors.affiliation: University of Parma, Institute of Pharmacology, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Bertaccini
authors.forename: G
authors.initials: G
authors.lastname: Morini
authors.forename: G
authors.initials: G
authors.lastname: Coruzzi
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D017259:Dimaprit / Q000494:pharmacology; D015738:Famotidine / Q000494:pharmacology; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology / Q000502:physiology*; D017442:Histamine Agonists / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D007422:Intestines / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012844:Sincalide / Q000494:pharmacology
chemical_list: D017442:Histamine Agonists; D006635:Histamine H2 Antagonists; D018727:Muscarinic Antagonists; D015738:Famotidine; D001285:Atropine; D006632:Histamine; D012844:Sincalide; D017259:Dimaprit