Pharmacologic relationship of antisaccade and dyskinesia in schizophrenic patients

Abnormalities in saccadic eye movements have been found in schizophrenics with tardive dyskinesia (TD). This finding supports accumulating evidence for a GABAergic dysfunction in the subcortical-cortical circuits controlling motor and oculomotor behavior. We found that in response to muscimol, a direct-acting GABA agonist, changes in the antisaccade error rate and dyskinesia score were strongly correlated. We then looked at the relationship between these measures during single-blind haloperidol withdrawal. Significant changes occurred in antisaccade error during drug withdrawal, but the final measure was not significantly different from the baseline assessment. Antisaccade error change scores were not correlated with dyskinesia change scores. Change score in antisaccade error was positively correlated with change on the Brief Psychiatric Rating Scale, specifically with the Anxiety/Depression factor. These findings suggest that GABAergic mechanisms are more robust than dopaminergic mechanisms in the pathophysiology of persistent tardive dyskinesia.