Studies on cutaneous vascular permeability in the rat: increases caused by histamine and histamine-like agents.

The pharmacology of histamine-induced increases in microvascular permeability has been studied in rat skin. Histamine caused dose-dependent increases in microvascular permeability, assessed as increases in extravascular albumin accumulation. The responses to histamine were inhibited in a dose-dependent manner by pretreatment with mepyramine and were not changed by cimetidine. 2-(2-Aminoethyl)pyridine also increased microvascular permeability whereas impromidine did not. These results suggest that H1-receptors and not H2-receptors are involved in the permeability response to histamine in rat skin. In contrast, dimaprit increased microvascular permeability and responses to dimaprit exceeded the maximum response to histamine. The response to dimaprit proved to be independent of H2 receptors and was consistent with an indirect response due to mast cell degranulation.