Modulation of apomorphine-induced stereotyped behavior by cholecystokinin.

1. The goal was to verify if central or peripheral sulphated cholecystokinin octapeptide (CCK8) injections can modulate apomorphine (APO)-induced stereotyped behavior. Experiments were designed to determine the involvement of cholecystokinin receptor subtypes as well. 2. Animals which received CCK8 (0.0725, 0.145 and 14.5 nmol, icv) showed a significant (p < 0.05) decrease in APO (0.6 mg/kg, sc)-induced stereotyped behavior. 3. No other statistically significant difference was observed among groups. Since ip CCK8 (1.16 or 2.32 nmol/kg) injections did not interfere with APO-induced stereotypy, the results suggest that the CCK8 modulatory effects have a central action. 4. The results also suggest that the effects of icv CCK8 were not due to the stimulation of CCK8 receptors alone since central CCK4 (14.5 or 29.0 nmol) injections did not interfere with the expression of stereotypy.