Effects of cholecystokinin octapeptide on striatal dopamine metabolism and on apomorphine-induced stereotyped cage-climbing in mice.

The effects of sulfated (CCK-8-SE) and non-sulfated (CCK-8-NS) cholecystokinin octapeptide on striatal dopamine (DA) metabolism have been investigated on mice. CCK-8-NS facilitated the disappearance of striatal DA, measured after synthesis inhibition with 350 mg/kg of alpha-methyl-p-tyrosine. CCK-8-SE did not affect DA disappearance. In vitro uptake of [3H]DA by striatal slices was affected by neither CCK-8-SE, nor CCK-8-NS (10(-5) M). Potassium-induced in vitro release of [3H]DA from striatal slices was significantly increased by 10(-5) M CCK-8-NS: however, CCK-8-SE likewise increased DA release in this model system. Apomorphine-induced (1.0 mg/kg) stereotyped cage-climbing behavior was not affected by CCK-8-SE but was enhanced by CCK-8-NS. This effect could be antagonized by haloperidol, but not by naloxone. The data suggest that CCK-8-NS affects striatal DA release, disappearance and receptor sensitivity in the mouse. Dopaminergic mechanisms should therefore be regarded as a possible mode of action of CCK-8-NS on brain functions.