INFLUENCE OF SEASON AND ANAESTHETIC ON CUTANEOUS VASCULAR PERMEABILITY RESPONSES TO HISTAMINE, SEROTONIN AND MAST CELL-RELEASING AGENTS IN RATS

The influences of season and anaesthetic on the cutaneous vascular permeability responses to histamine (2.5 X 10(-8) mol), serotonin (5HT, 2.5 X 10(-10) mol), and to the mast cell-releasing agents adenosine 5(1)-triphosphate (2.5 X 10(-7) mol), dextran (5 X 10(-5) g) and compound 48/80 (1 X 10(-7) g) were examined using an Evans blue dye leakage technique. In rats anaesthetized with urethane (1 g/kg i.p.), responses to irritants were significantly less than in rats given ether for the period of administration of irritants and allowed to recover consciousness. The response to histamine was mediated by H1-receptors since it was abolished by mepyramine but not by metiamide. The only seasonal variation observed was in responses to 5HT in urethane-anaesthetized rats, which were significantly less in winter than in summer. It was concluded that dye leakage responses to irritants are affected more by anaesthetic than by seasonal variation.