Chronic amphetamine administration decreases brain tryptophan hydroxylase activity in cats

Michael E. Trulson, Barry L. Jacobs

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Chronic administration of d-amphetamine sulfate (7.5 mg/kg, i.p. every 12 hrs. for 6 days) to cats produced significant decreases in the Vmax of brain-stem and forebrain tryptophan hydroxylase when measured 1 day (-34 and -46%) and 10 days (-17 and -30%) after the final amphetamine injection. Serotonin and 5-hydroxyindoleacetic acid (5HIAA) levels were decreased by a similar magnitude. A single injection of amphetamine (7.5 mg/kg) produced no significant changes in tryptophan hydroxylase activity, serotonin, or 5HIAA when measured 1 day after the injection. Neither acute nor chronic amphetamine treatment produced any significant changes in the Km of tryptophan hydroxylase for either tryptophan or the natural co-factor, tetrahydrobiopterin. These data suggest that chronic amphetamine treatment decreases central serotonergic neurotransmission by an action on the rate-limiting enzyme in serotonin biosynthesis.

Original languageEnglish (US)
Pages (from-to)329-335
Number of pages7
JournalLife Sciences
Issue number5
StatePublished - Feb 4 1980

All Science Journal Classification (ASJC) codes

  • General Pharmacology, Toxicology and Pharmaceutics
  • General Biochemistry, Genetics and Molecular Biology


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