title: Narcotic drugs: effects on the serotonin biosynthetic systems of the brain.
abstract: The effects of short- and long-term administration of morphine on the activity of two measurable forms of rat brain tryptophan hydroxylase were studied. Morphine administration produced an immediate decrease and a longterm increase in the nerve ending (particulate) enzyme activity but did not change the cell body (soluble) enzyme activity. Cocaine administration demnonstrated a short-term decrcease in measurable nerve eniding enzyme activity that was due to the inhibition of the high affinity uptake (the Michaelis constant, K(m) is 10-(5) molar) of trytophan, the serotonin precursor. Cocaine did not aflect the low affinity uptake K(m) = 10-(5) molar) of tryptophan. Both the uptake of the precursor and the enizymiie activity appeared to be drug-sensitive regullatory processes in the biosynthlesis of serotonin.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D002247:Carbon Isotopes; D003042:Cocaine / Q000494:pharmacology*; D008297:Male; D008636:Mesencephalon / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000032:analysis*; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009411:Nerve Endings / Q000201:enzymology; D051381:Rats; D012701:Serotonin / Q000096:biosynthesis*; D013572:Synaptic Vesicles / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism; D013997:Time Factors; D014364:Tryptophan / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D012701:Serotonin; D009020:Morphine; D014364:Tryptophan; D006899:Mixed Function Oxygenases; D003042:Cocaine