Morphine-Induced Changes in the Activity of Enzymes Involved in Neutrotransmitter Metabolism in Specific Brain Regions of the Tolerant Rat
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
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The activities of choline acetyl transferase E.C.220.127.116.11., acetylcholinesterase E.C.18.104.22.168. and monoamine oxidase E.C.22.214.171.124. were determined in the hippocampus, thalamus, hypothalamus, cerebral cortex and basal ganglia of groups of rats sacrificed at predetermined times following the last scheduled morphine injection. It was found that, in animals that showed a paradoxical activation reaction shortly after the last morphine injection jumping rats, monoamine oxidase activity decreased in all brain areas studied with lowest values between approximately 30 and 60 minutes, and returned to nearly normal values by six hours postinjection. Acetylcholinesterase activity showed oscillations above control values. Oscillating changes were also observed in the activity of choline acetyl transferase depending on the time of sacrifice of the animal. No appreciable changes in monoamine oxidase activity were observed in nonjumping tolerant rats.