Neuroleptics produce within‐session response decrements: Facts and theories

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Abstract
Acute neuroleptic administration results in within‐session decrements for conditioned active avoidance, discriminated lever release (reaction time), fixed‐ratio responding, lever pressing for intracranial electrical stimulation, licking, runway running, and treadmill running. Similarly, catalepsy has been shown to be increased by repeated testing. This paper briefly reviews these findings and reports new results on the effects of haloperidol on the micro‐characteristics of rats' operant behavior maintained by fixed‐ratio 20 food reinforcement. With these methods, within‐session decrements were seen to be produced by abrupt cessation of responding and by response slowing that was evident from the first few responses in the session. It is argued that within‐session decrements can be viewed as manifestations of neuroleptic‐induced pseudoparkinsonism in the rat and that dynamic neurochemical changes in the nigrostriatal dopamine system mediate the behavioral changes.