AJP - Heart and Circulatory Physiology, Vol 232, Issue 1 73-H78, Copyright © 1977 by American Physiological Society
Action of histamine and H1 and H2 blockers on the cardiopulmonary circulation
J. R. Woods Jr, C. R. Brinkman, A. Dandavino, K. Murayama and N. S. Assali
Systemic and pulmonary hemodynamic responses to histamine were investigated
inchronically instrumented unanesthetized nonpregnant ewes. Histamine was
administered intravenously and into the pulmonary artery. The effects of
the same doses of histamine were assessed following H1 and H2 receptor
blockade. The effects ocular changes were also monitored. Results indicate
that intravenous histamine produces tachycardia, systemic hypotension,
pulmonary hypertension, and reduced cardiac output. The pulmonary response
could be modified significantly by pentobarbital anesthesia. When injected
directly into the pulmonary artery histamine failed to elicit any
circulatory response. Blockade of H1 and H2 receptors, as well as autonomic
ganglia, resulted in a comparable attentuation of the histamine circulatory
response. It is concluded that a) central hemodynamic responses do not seem
to be mediated through specific H1 and H2 receptors; b) histamine-induced
pulmonary vasoconstriction can be reversed by pentobarbital anesthesia, and
c) the absence of circulatory response to intrapulmonary histamine
administration suggests that whatever receptors that may exist in the
pulmonary vascular bed are not necessary for the central hemodynamic
effects.
