Peripheral stimulation of CCK-B receptors by BC264 induces a hyperexploration, dependent on the partial derivative opioid system in the nucleus accumbens of rat

This study analyses the influence of the CCKergic system on the enkepharine rgic system in the exploratory behavior of rats, using both behavioral and biochemical approaches. The results show that the increase of the spontaneo us alternation behavior induced by the selective CCRB agonist, BC264 (3 mu g/kg) was not suppressed by the opioid antagonists, naloxone (100 mu g/kg), or naltrindole (300 mu g/kg). In contrast, BC264 injected at the same dose induced a hyperlocomotor activity measured in the open-field test, which w as antagonized by the selective a opioid antagonist, naltrindole. BC264(3 m u g/kg) significantly increased the extracellular levels of Met-LI in the a nterior part of the nucleus accumbens. Furthermore, local injection of nalt rindole (0.25 mu g;0.5 mu l) in the anterior nucleus accumbens completely s uppressed the hyperlocomotion induced by BC264. The behavioral effects indu ced by BC264 cannot be explained by its interaction with gastrinic receptor s mediating gastric acid release, since BC264 produced a long-lasting incre ase of gastric acid output from conscious gastric fistula rats only at dose s 100 times higher than those inducing behavioral modifications. The hyperl ocomotion obtained after stimulation by BC264 of probably peripheral CCRB r eceptors, indicates that this receptor type could participate in the transm ission of information between the peripheral system and some regions of the CNS involved in motivations and emotions. (C) 1999 Elsevier Science Ltd. A ll rights reserved.