Dopamine, neuroleptics and reinforced behavior

Area of Science:

• Neuroscience
• Behavioral Pharmacology
• Psychopharmacology

Background:

• Dopamine antagonist neuroleptic drugs cause significant reductions in operant performance across various positive reinforcers.
• Existing hypotheses attribute this impairment to either anhedonic (reward-related) or motoric deficits following dopamine antagonism.

Purpose of the Study:

• To investigate the precise nature of behavioral impairment induced by dopamine antagonist neuroleptic drugs.
• To differentiate between motor and reward-related effects of these drugs using novel behavioral paradigms.

Main Methods:

• Assessed motor performance using a force-transducer in a food-reinforced operant task to analyze biophysical properties of responding.
• Employed three distinct paradigms in undrugged animals to study reward impairments: partial reinforcement extinction, incentive motivation, and conditioned place preference tests.

Main Results:

• Neuroleptic challenge impaired the temporal aspects ('timing') of operant behavior, not the physical capacity ('force') to respond.
• Behavioral patterns in undrugged animals, when motor confounds were eliminated, mimicked effects of reduced reward magnitude.
• Data indicate that dopamine antagonist drugs impact operant behavior in ways consistent with reward processing alterations.

Conclusions:

• Central dopaminergic substrates play a crucial role in the neurobiology of positive reinforcement.
• Dopamine antagonism primarily affects the timing of behavior, suggesting a significant role in reward valuation rather than motor output.