FETAL AND NEONATAL CARDIOPULMONARY RESPONSE TO HISTAMINE

  • 1 January 1976
    • journal article
    • research article
    • Vol. 48  (2) , 195-202
Abstract
Effects of i.v. histamine and its H1 receptor blocker (Benadryl) were investigated in near-term fetal and in newborn lambs. Fetuses were studied before and after closure of the ductus arteriosus. Newborn lambs were chronically instrumented and the same animal was tested periodically from 3-70 days old. In the fetus whose pulmonary bascular resistance in already high, histamine produces a profound pulmonary vasodilatation. In the neonate with reduced pulmonary vascular resistance, histamine produces pulmonary vasoconstriction similar to that of the adult. Both responses can be attenuated by Benadryl indicating that they are mediated by the same receptor. In the fetus, histamine produces marked constriction of the ductus arteriosus which could be partly attributed to the pulmonary vasodilatation. When neonatal pulmonary vascular resistance was raised by hypoxia, histamine elicited a biphasic response, partially blocked by Benadryl. These findings are discussed in terms of their possible role in cardiovascular and pulmonary changes that occur after birth.