Influence of halothane and methoxyflurane on regional brain and spinal cord concentrations of methionine-enkephalin in the rat.
Rats were exposed to either oxygen (controls), 1.5% halothane in oxygen, or methoxyflurane (0.5%) in oxygen over a period of 2 h, then sacrificed at the end of exposure (2-h group), 4 h after removal from environmental chamber (4-h group), or at 24 h following anesthetic exposure (24-h group). Pituitary (excluding the neural lobe, Pit), brain, and spinal cord areas were isolated and processed with Met-enkephalin tissue concentrations determined. In halothane-exposed animals, Met-enkephalin concentrations in pit and across CNS areas studied were significantly lower at 2 h following anesthetic exposure than in control animals. Concentrations of Met-enkephalin in many areas of CNS and Pit of 4-h group approached control levels. Concentrations of Met-enkephalin in all areas studied except spinal cord returned to basal levels by 24 h following halothane exposure. Exposure to methoxyflurane resulted in less dramatic changes in Met-enkephalin concentrations across CNS regions examined. Exposure to methoxyflurane resulted in significant decreases in Met-enkephalin levels in olfactory bulb, thalamus, and hippocampus only. Met-Enkephalin levels did not change significantly in other areas of the central nervous system following methoxyflurane exposure. These results indicate that halothane and methoxyflurane may have differential effects on the endogenous opioid system.
Agarwal
R K
RK
Department of Anatomy and Cellular Biology, Tufts University School of Veterinary Medicine, N. Grafton, MA 01536.
Court
M
M
Chandna
V K
VK
Mohan
A
A
Engelking
L R
LR
Kumar
A M
AM
D000818:Animals; D001921:Brain / Q000187:drug effects*; D004744:Enkephalin, Methionine / Q000378:metabolism*; D006221:Halothane / Q000494:pharmacology*; D008297:Male; D008733:Methoxyflurane / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000187:drug effects*
D008733:Methoxyflurane; D004744:Enkephalin, Methionine; D006221:Halothane