Neuroleptic influences on a lateralized behavioral bias in unoperated rats

Abnormalities of the ascending dopaminergic system have been associated with hemineglect, and evidence suggests that neuroleptic treatments normalize the right hemispatial attentional impairment that is sometimes observed in acutely psychotic schizophrenic patients.

A research program was initiated to develop an animal model of hemineglect-drug interactions.

Female rats were tested repeatedly on removing a "nuisance stimulus" - strips of surgical tape applied loosely to the forelimbs. Subjects were assigned to groups dependent upon showing a behavioral orientation preference (BOP) during pre-drug baseline tests. Animals representing left-BOP, right-BOP and no preference continued to be tested during chronic exposure either to a dopamine antagonist (0.05 mg haloperidol/kg) or agonist (1.0 mg d-amphetamine/kg) or vehicle only.

Three weeks of haloperidol treatments to rats only with an initial right BOP gradually eliminated the response bias, as revealed by declines in choosing the right forepaw and the latencies between attending to the two forepaws.

The results recommend right BOP female rats as a simple, non-invasive behavioral animal model for evaluating and comparing neuroleptic medications.