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Psychopharmacology

, Volume 76, Issue 1, pp 29–35 | Cite as

Discriminative stimulus properties of l-5-hydroxytryptophan: Behavioral evidence for multiple serotonin receptors

  • Robert J. Barrett
  • M. Ann Blackshear
  • Elaine Sanders-Bush
Original Investigations

Abstract

Rats were trained to discriminate the stimulus properties of l-5-hydroxytryptophan (l-5-HTP) (30 mg/kg SC), the immediate precursor of serotonin (5-HT). The peripheral decarboxylase inhibitor R04-4602, administered prior to l-5-HTP, greatly attenuated the disruptive effects observed on responding when l-5-HTP alone was injected. Following acquisition, the discrimination was dosedependent and generalized to fenfluramine, a 5-HT-releasing drug, but not to amphetamine, a catecholamine-releasing agent. Further evidence for the involvement of 5-HT receptor stimulation in mediating the discrimination was that pretreatment with fluoxetine, a highly specific 5-HT uptake inhibitor, markedly potentiated the cue. Nevertheless, the classical 5-HT antagonists methysergide, cyproheptadine, metergoline, and methiothepin did not block the l-5-HTP-related discriminative stimulus. This finding suggested that the cue properties of l-5-HTP might be mediated by a population of 5-HT receptors previously identified electrophysiologically in limbic structures. As in the present experiment, the putative 5-HT antagonists did not block the synaptic effects of 5-HT in these structures.

Key words

l-5-HTP Serotonin antagonists Drug discrimination Multiple serotonin receptors 

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Copyright information

© Springer-Verlag 1982

Authors and Affiliations

  • Robert J. Barrett
    • 1
  • M. Ann Blackshear
    • 2
    • 3
  • Elaine Sanders-Bush
    • 2
    • 3
  1. 1.Veterans Administration Medical Center and Departments Psychology and PharmacologyVanderbilt UniversityNashvilleUSA
  2. 2.Department of PharmacologyVanderbilt University School of MedicineNashvilleUSA
  3. 3.Tennessee Neuropsychiatric InstituteNashvilleUSA

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