TABLE 1. Serotonergic agents used in neuroendocrine studies in schizophrenia

Test agent

Receptor occupied (agonist/




5-HT1C5-HT1D, 5-HT2 (weak agonist),

5-HT6, 5-HT7,

Diminished PRL reponse compared to controls

mCPP 5-HT 1C, 5-HT 1D,5-HT2(weak agonist),

5-HT6, 5-HT7

Diminished cortisol response sompared to controls
L-Tryptophan All 5-HT receptors activated No difference in PRL response compared to controls
Fenfluramine All 5-HT receptors activated Diminished PRL response compared to controls
MK-212 5-HT2c, 5-HT2A 5-HT1A (?) Diminished temperature response compared to


MK-212 + clozapine 5-HT2, 5-HT1c activated; 5HT2,

5-HT1c, 5HT6, 5-HT7 blocked

Blocked PRL and cortisol response to MK-212
Fenfluramine + clozapine All 5-HT receptors activated; 5-HT2,

5-HT1c, 5-HT6, 5-HT7 blocked

Blocked PRL response to fenfluramine
L-Tryptophan + typical


All 5-HT receptors activated; D2

receptors blocked

Augmented PRL response to L-tryptophan

Diminished GH response

Cimetidine 5-HT2 activated (indirect) Diminished PRL response in schizophrenia

compared to control

Cimetidine + clozapine 5-HT2 activated (indirect); 5-HT2,

5-HT1c, 5HT6, 5-HT7 blocked)

Clozapine abolishes the PRL response induced by


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published 2000