The serotonin-1A receptor antagonist WAY-100635 modifies fluoxetine's antidepressant-like profile on the differential reinforcement of low rates 72-s schedule in rats.
BACKGROUND
Recent preclinical and clinical data suggest that co-administration of a serotonin-1A (5-HT-1A) receptor antagonist with an antidepressant drug has greater therapeutic efficacy than when the antidepressant drug is administered alone.


OBJECTIVE
The purpose of the present experiment was to determine whether pretreatment with the selective 5-HT-1A receptor antagonist N-[2-[4-(2-methoxyphenyl)- 1-piperazinyl]ethyl]-N-(pyridinyl)cyclohexanecarboxamide (WAY-100635; 0.003, 0.03, 0.3 mg/kg, s.c.) would alter the effects of the antidepressant fluoxetine (2.5-10 mg/kg, i.p.) on the differential reinforcement of low-rate 72-s (DRL 72-s) schedule. The DRL 72-s schedule is a behavioral screen selective and sensitive to antidepressant drugs.


RESULTS
WAY-100635 had no behavioral effects on its own. The lower doses of fluoxetine (2.5 mg/kg and 5 mg/kg) had no effects, but 10 mg/kg increased reinforcement rate without affecting response rate. The increase in reinforcement rate was blocked by pretreatment with 0.03 mg/kg and 0.3 mg/kg WAY-100635, although the combination of fluoxetine and WAY-100635 also significantly reduced response rate. Interestingly, 0.003 mg/kg or 0.03 mg/kg WAY-100635 administered with 5.0 mg/kg fluoxetine increased reinforcement rate, even though this dose of fluoxetine had no effect on performance.


CONCLUSIONS
These data demonstrate that the behavioral effects of fluoxetine are modified by 5-HT-1A receptor blockade.
Department of Pharmacological and Physiological Sciences, University of Chicago, IL 60637, USA.
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Cousins
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Seiden
D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005473:Fluoxetine / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects*; D044263:Receptors, Serotonin, 5-HT1; D012055:Reinforcement Schedule; D012702:Serotonin Antagonists / Q000494:pharmacology*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology*
D005473:Fluoxetine; D010879:Piperazines; D011725:Pyridines; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists; D017367:Selective Serotonin Reuptake Inhibitors; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide