Nature of histamine receptors concerned in capillary permeability.

1 Histamine and 2-methyl-histamine (H1-receptor agonist) caused dose-dependent increases in capillary permeability in albino mice, but 4-methyl-histamine (H2-receptor agonist) caused no significant increase. 2 Mepyramine (H1-receptor antagonist) blocked the histamine-induced increase in capillary permeability whereas burimamide (H2-receptor antagonist) produced no significant blockade of the histamine-response. 3 Combined mepyramine and burimamide pretreatment did not give any significantly greater protection than mepyramine alone. 4 The results indicate involvement of the H1-receptors in histamine-induced increase in capillary permeability.