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NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Ketamine inhibits fetal ACTH responses to cerebral hypoperfusion

Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gaineseville, Florida

Submitted 4 May 2006 ; accepted in final form 4 December 2006

The present study tested the effect of ketamine on the fetal reflex responses of late-gestation sheep to brachiocephalic occlusion (BCO), a stimulus that mimics the reduction in cerebral blood flow that results from severe fetal hypotension. Ketamine, a dissociative anesthetic and known noncompetitive antagonist of N-methyl D-aspartate (NMDA) receptors, has previously been shown to impair chemoreceptor responsiveness. Studies from this laboratory suggest that fetal reflex ACTH responses to hypotension are largely mediated by chemoreceptors; therefore, we hypothesized that ketamine would inhibit the reflex hormonal response to BCO. Chronically catheterized fetal sheep were subjected to acute cerebral hypoperfusion through occlusion of the brachiocephalic artery. Fetal blood pressure and heart rate were continuously recorded, and fetal blood samples drawn during the experiment were analyzed with specific hormone assays. Our results demonstrate that ketamine attenuates hemodynamic responses to cerebral hypoperfusion and is a potent inhibitor of ACTH and proopiomelanocortin (POMC)/pro-ACTH release. These data support the hypothesis that fetal reflex responses hypotension are chemoreceptor mediated. Given the potency with which ketamine inhibits ACTH response to fetal hypotension, we suggest that the use of ketamine or other anesthetic or analgesic drugs that block or otherwise interact with the NMDA-glutamate pathways, in late pregnancy or in preterm newborns be reconsidered.

chemoreceptor; baroreceptor; adrenocorticotropin; proopiomelanocortin; NMDA; glutamate

This article has been cited by other articles:

				C. E. Wood, M. Powers Fraites, and M. Keller-Wood Blockade of PGHS-2 inhibits the hypothalamus-pituitary-adrenal axis response to cerebral hypoperfusion in the sheep fetus Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2009; 296(6): R1813 - R1819. [Abstract] [Full Text] [PDF]