Cholecystokinin octapeptide levels in rat brain are changed after subchronic neuroleptic treatment.

Cholecystokinin octapeptide sulfate (CCK-8-S), nonsulfated cholecystokinin octapeptide (CCK-8-NS) and cholecystokinin tetrapeptide (CCK-4) levels in rat brain were measured by a combination of high pressure liquid chromatography (HPLC) and radioimmunoassay (RIA) after acute and subchronic treatment of the animals with haloperidol. CCK levels did not change after acute treatment. However, CCK-8-S concentrations were increased in the striatum and the mesolimbic system after two weeks of haloperidol treatment and remained increased after four weeks of haloperidol treatment. A transient decrease in CCK-8-S concentrations was observed in the cortex. Treatment with chlorpromazine or clozapine gave similar results. No changes in CCK-8-NS or CCK-4 concentrations were seen in any of the experiments.