Differentiation between the stimulus effects of 1-5-hydroxytryptophan and LSD

Kathryn A. Cunningham, Patrick M. Callahan, James B. Appel

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


The stimulus properties of the serotonin precursor 1-5-hydroxytrptophan (5-HTP) and the hallucinogen d-lysergic acid diethylamide (LSD) were compared in a two-lever, water-reinforced drug discrimination task. 5-HTP (in combination with the peripheral decarboxylase inhibitor Ro 4-4602) elicited no more than 50% drug-lever responding in rats trained to discriminate LSD (0.08 mg/kg) from saline while LSD substituted completely in animals trained to discriminate 5-HTP (50 mg/kg) from saline. Combination tests indicated that, while the 5-HTP cue was unaffected by pretreatment with various serotonin antagonists, the substitution of LSD for 5-HTP was abolished by the putative serotonin-2 antagonist ketanserin. It was concluded that LSD mimics 5-HTP by stimulating a subset of serotonin receptors activated by 5-HTP which are sensitive to ketanserin (serotonin-2?).

Original languageEnglish (US)
Pages (from-to)179-186
Number of pages8
JournalEuropean Journal of Pharmacology
Issue number2
StatePublished - Jan 22 1985
Externally publishedYes


  • 1-5-Hydroxytryptophan
  • Drug discrimination
  • Serotonin (5-hydroxytryptamine)
  • d-Lysergic acid diethylamide (LSD)

ASJC Scopus subject areas

  • Pharmacology


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