Some Cardiorespiratory Effects of Histamine, 5-Hydroxytryptamine, and Compound 48/80 in the Calf

Abstract

The cardiorespiratory responses to histamine, 5-hydroxytryptamine, and compound 48/80 have been examined in the calf. The simultaneous measurement of whole blood histamine and plasma 5-hydroxytryptamine during compound 48/80 infusion showed significantly elevated levels that followed a biphasic pattern. However, mast cell changes in the sites examined were minimal and there was no significant difference in histamine concentrations in tissues examined. Marked systemic effects were observed and included an initial rise in femoral arterial blood pressure which was later followed by a terminal hypotension and death. Pulmonary arterial blood pressure and venous pressure were both elevated and dyspnoeic respiration was also evident. A combination of mepyramine and methysergide inhibited the toxicity of compound 48/80 which suggested that histamine and 5-hydroxytryptamine played a major role in the toxic response to this substance in the calf.