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Chronic haloperidol treatment: effects on operant responding and inter-response time
Insights
Haloperidol administration significantly reduced food reinforcement in rats when given before operant behavior sessions. This suggests anhedonia, not motor deficits, may explain haloperidol
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- Haloperidol is a typical antipsychotic.
- Its effects on operant behavior are not fully understood.
- Motor deficits and anhedonia are potential mechanisms of action.
Purpose of the Study:
- To investigate the effects of haloperidol on operant behavior in rats.
- To differentiate between anhedonia and motor deficits as explanations for haloperidol's effects.
Main Methods:
- Male Sprague-Dawley rats were trained on a fixed ratio-40 schedule for food reinforcement.
- Rats received three doses of haloperidol (0.125, 0.25, 0.5 mg/kg) under various treatment regimens (Baseline, Presession, Postsession, Extinction).
- Inter-response times were measured.
Main Results:
- Presession and Extinction treatments significantly decreased earned reinforcements.
- Increased inter-response times correlated with decreased reinforcements.
- Presession treatment, but not Postsession, significantly reduced reinforcements.
Conclusions:
- Chronic presession haloperidol administration impairs operant behavior.
- Results favor an anhedonia interpretation over cumulative motor deficits.
- Concurrent exposure to haloperidol and behavior is critical for observed decrements.
Abstract:
Three groups (n = 6) of male Sprague-Dawley rats were trained to barpress for food reinforcement on a fixed ratio-40 schedule. Each group then received one of three doses of haloperidol (0.125, 0.25, or 0.5 mg/kg, i.p.) according to the following treatment regimen: Baseline, Presession, Postsession, Presession, Postsession, Baseline, Extinction. Each treatment lasted six days each. Only the Presession and Extinction conditions resulted in a significant decrease in the number of reinforcements earned. The number of inter-response times greater than ten sec was inversely related to the number of reinforcements earned. The fact that chronic presession, but not postsession treatment, significantly decreased the number of reinforcements earned would favor an anhedonia interpretation over one postulating cumulative motor deficits. In any event, prior concurrent experience with the drug effect and the operant behavior appears to be critical to the decrement induced by haloperidol.