Changes in striatal dopamine metabolism during precipitated morphine withdrawal.
Precipitation of withdrawal in morphine tolerant/dependent rats by either naloxone or the partial agonist ZK 48491 caused a significant increase in the contration of striatal DA, which persisted for at least 1 h. During the same time the probenecid-induced accumulation of HVA and DOPAC was reduced in the striatum in relation to probenecid-treated tolerant/dependent controls. 20 min after precipitation of withdrawal by naloxone, the striatal concentration of 3-methoxytyramine was decreased by about 40%, while the activity of the DA metabolizing enzymes, MAO and COMT, remained unchanged. Naloxone-precipitated withdrawal was, further, found to delay the depletion of striatal DA caused by inhibition of synthesis 90 min after alpha-methyl-p-tyrosine treatment. All these results provide evidence for a decreased release of DA from the striatum during precipitated morphine withdrawal.
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001575:Benzomorphans / Q000031:analogs & derivatives / Q000494:pharmacology; D002394:Catechol O-Methyltransferase / Q000378:metabolism; D003342:Corpus Striatum / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D004298:Dopamine / Q000096:biosynthesis / Q000378:metabolism*; D006719:Homovanillic Acid / Q000378:metabolism; D006801:Humans; D008297:Male; D008995:Monoamine Oxidase / Q000378:metabolism; D009020:Morphine; D009270:Naloxone / Q000494:pharmacology; D011339:Probenecid / Q000494:pharmacology; D051381:Rats; D013375:Substance Withdrawal Syndrome / Q000139:chemically induced / Q000378:metabolism*; D013997:Time Factors; D014439:Tyramine / Q000031:analogs & derivatives / Q000378:metabolism
D001575:Benzomorphans; D015102:3,4-Dihydroxyphenylacetic Acid; D009270:Naloxone; D009020:Morphine; D008995:Monoamine Oxidase; D002394:Catechol O-Methyltransferase; D011339:Probenecid; D004298:Dopamine; D006719:Homovanillic Acid; D014439:Tyramine