Influence of isoflurane on enkephalin levels and on some indicatory enzymes in the central nervous system of rabbits.

: The objective of this study was to analyse the effects of isoflurane anesthesia (lasting for 15 or 60 min) and isoflurane anesthesia termination (after 1 or 24 h) on met-enkephalin (MENK) and leu-enkephalin (LENK) levels in discrete brain areas and spinal cord segments in rabbits. Moreover histochemical analysis of activities of succinate dehydrogenase, magnesium-dependent adenosine triphosphatase (Mg++ATP-ase) and acid phosphatase in the striatum and hypothalamus were carried out to evaluate the effects of isoflurane anesthesia on energetic, transport and catabolic processes. Throughout anesthesia (15 and 60 min) and after its termination (1 h) the LENK contents were increased in hypothalamus, hippocampus, mesencephalon and lumbar segment of spinal cord. Moreover, during isoflurane anesthesia and after its termination (1 h) MENK and LENK levels decreased in cervical segment and MENK content dropped in thoracic segment of spinal cord. Histochemical data indicated, that isoflurane enhanced energetic processes as well as exchange processes in neurocytes, glial cells, capillary walls and ependymal cells of the third ventricle. Measurements of acid phosphatase activity provided evidence of no signs of toxicity of isoflurane in the examined areas. The changes in enkephalin levels observed during the isoflurane anesthesia and after its termination depended on the type of examined neuropeptides, as well as on parts of the brain and spinal cord studied. The changes observed after isoflurane administration in enkephalinergic system are discussed with regard to our earlier experiments with halothane and enflurane.