spasmogenic action of histamine , 2- ( 2-aminoethyl ) pyridine ( h1 receptor agonist ) and 4 methyl-histamine ( h2 receptor agonist ) , have been studied in guinea pig isolated urinary bladder in the presence of mepyramine ( h1 antagonist ) and metiamide ( h2 antagonist ) to identify the presence of h1 and h2 receptors .
C0019588
histamine
C0025779
methyl-histamine