Effects of halothane and methoxyflurane on the hypothalamic-pituitary-adrenal axis in rat

Effects of acute exposure (2 h) to either 1.5% halothane or 0.5% methoxyflu rane on chemical mediators of the hypothalamic-pituitary-adrenal (HPA) axis were evaluated in male Sprague-Dawley rats immediately after exposure, aft er the righting reflex (4 h), or 24 h postexposure. Effects of these anesth etics on hippocampal corticotropin releasing factor (CRF) were also evaluat ed, Methoxyflurane caused significant elevations in pituitary adrenocortico tropin hormone (ACTH)-like immunoreactivities in all three of the experimen t's time groups, yet halothane failed to cause the same response immediatel y after exposure, Serum ACTH-like immunoreactivities were significantly ele vated immediately after exposure to both anesthetics, but were not elevated at 4 and 24 h postexposure. Corticosterone (CORT)-like immunoreactivities were significantly elevated by halothane in all experimental groups, and in the 2- and 24-h groups following methoxyflurane exposure. Hippocampal CRF- like immunoreactivities remained unaffected by either anesthetic, Results i ndicate that a 2-h exposure to either halothane or methoxyflurane results i n significant activation of the rat hypothalamic-pituitary-adrenal axis, an d that the activation appears to be sustained over a 24-h period, (C) 1998 Elsevier Science Inc.