CONSTANT RATE INFUSION OF DEUTERATED PHOSPHORYLCHOLINE TO MEASURE EFFECTS OF MORPHINE ON ACETYLCHOLINE TURNOVER RATE IN SPECIFIC NUCLEI OF RAT BRAIN

By using constant rate infusion of deuterated phosphorylcholine the turnover rate of acetylcholine in nucleus accumbens, n. septi, n. interpeduncularis, n. raphes dorsalis, substantia nigra, cortex, hippocampus (regio superior) and n. caudatus was measured. A dose of morphine which is the effective median dose for analgesia, failed to change the steady-state of choline and acetylcholine in the above-mentioned nuclei, but it lowered the turnover rate of acetylcholine in hippocampus, cortex and n. accumbens. The action of morphine on acetylcholine turnover rate could be antagonized by naltrexone, which per se failed to change the steady-state of acetylcholine and choline or of acetylcholine turnover rate. The possibility that opiate receptor activation in n. accumbens through inhibition of the turnover rate of acetylcholine triggers a series of events that cause analgesia and/or catatonia is discussed.