Induced enzyme release from synaptosomes by halothane

Inhaled anesthetics elicit region-specific changes in protein expression in mammalian brain

Inhaled anesthetics bind specifically to many proteins in the mammalian brain. Within the subgroup of proteins whose activity is substantially modulated by anesthetic binding, it is reasonable to expect anesthetic-induced alterations in host expression level. Thus, in an attempt to define the group of functional targets for these commonly used drugs, we examined changes in protein expression after anesthetic exposure in both intact rodent brains and in neuronal cell culture. Differential in-gel electrophoresis was used to minimize variance, in order to detect small changes. Quantitative analysis shows that 5 h exposures to 1 minimum alveolar concentration (1 MAC) halothane caused changes in the expression of approximately 2% of detectable proteins, but only at 2-24 h after awakening, and only in the cortex. An equipotent concentration of isoflurane altered the expression of only approximately 1% of detectable proteins, and only in the hippocampus. Primary cortical neurons were exposed to three-fold higher concentrations of anesthetics with no evidence of cytotoxicity. Small changes in protein expression were elicited by both drugs. Despite the fact that anesthetics produce profound changes in neurobiology and behavior, we found only minor changes in brain protein expression. A pronounced degree of regional selectivity was noted, indicating an under appreciated degree of specificity for these promiscuous drugs.

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.

Utilization of Barritt color reaction for studying synaptosomal creatine phosphokinase

The assay for creatine phosphokinase activity depending upon the color formation from creatine was reinvestigated. Its sensitivity was improved to 5 nmol of creatine. The method gave satisfactory Michaelis constants for both creatine phosphate and adenosine-diphosphate and was useful in detecting low creatine phosphokinase activity.