Effects of morphine on the turnover of brain catecholamines and serotonin in rats-acute morphine administration.
Morphine increased the rate of brain dopamine (DA) depletion when given before alpha-methyl-p-tyrosine (AMT) or alpha-propyl-dopacetamide, but not when given after AMT. No effect of morphine was found on the rate of depletion of brain noradrenaline (NA) or serotonin (5-HT) after the two synthesis inhibitors. The accumulation of homovanillic acid and 5-hydroxy-indoleacetic acid induced by probenecid was significantly increased by morphine pretreatment, whereas the accumulation of 3-methoxy-4-hydroxy-phenylglycol sulphate was not changed. These findings can be best explained by the hypothesis that morphine increases the non-functional intraneuronal catabolism of newly synthesized DA and 5-HT, without much effect on the monoamines already taken up in the synaptic vesicles. NA turnover does not seem to be changed by acute morphine administration.
D015098:3-Methoxy-4-hydroxyphenylethanol / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D006719:Homovanillic Acid / Q000378:metabolism; D008297:Male; D008781:Methyltyrosines / Q000494:pharmacology; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D011339:Probenecid / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000378:metabolism*; D013997:Time Factors
D002395:Catecholamines; D008781:Methyltyrosines; D015098:3-Methoxy-4-hydroxyphenylethanol; D012701:Serotonin; D009020:Morphine; D011339:Probenecid; D004298:Dopamine; D009638:Norepinephrine; D006719:Homovanillic Acid