The influence of laboratory anaesthetics on the increased cutaneous vascular permeability responses to histamine and 5-hydroxytryptamine in rats.

The effect of several anaesthetic regimens on the increased cutaneous vascular permeability response to histamine and 5-hydroxytryptamine (5HT) was investigated in rats, using the Evans blue dye leakage technique. Diethyl ether administered during injections (2-3 minutes) or urethane 1000 mg/kg did not significantly affect responses to either histamine or 5HT compared with responses obtained in rats given no anaesthetic. However ether administered for 10 or 20 minutes significantly increased the response to histamine. All other anaesthetic regimens tested (urehtane 1250 mg/kg, urethane-chloralose, urethane-pentobarbitone, pentobarbitone, pentobarbitone-xylazine, pentobarbitone-chloralose) reduced responses to histamine and/or 5HT. It was concluded that urethane (1000 mg/kg), although it does not produce full surgical anaesthesia, is the most satisfactory alternative to the use of unanaesthetized animals for dye leakage studies in rats.