Modulation of the inflammatory response to histamine by terbutaline and sodium nitroprusside in guinea-pig skin

We measured the microvascular response (vasodilatation and plasma exudation) to skin prick provocations with histamine, terbutaline, sodium nitroprusside (SNP) and the combinations of terbutaline and histamine as well as SNP and histamine in guinea-pig skin. The response was measured by external detection of beta radiation from transferrin labelled with In-113m. Histamine induced a moderate microvascular response. Terbutaline alone induced a smaller response, probably reflecting vasodilatation. When added to histamine, terbutaline significantly reduced the microvascular response to histamine. The response to histamine, SNP and the combination of histamine and SNP were all similar. We conclude that the anti-inflammatory effect of terbutaline can be readily measured with this technique. We found no indication of a pro-inflammatory effect of SNP when combined with histamine. Rather, the lack of additive effect may suggest an anti-inflammatory effect of SNP on the response to histamine.