CCK8 effects on motivational and emotional states of rats involve CCKA receptors of the postero-median part of the nucleus accumbens.

Administration of 3 fmol of cholecystokinin octapeptide (CCK8) into the postero-median nucleus accumbens (NAS) induced an hypoexploration measured using the four-hole box and an increase in the emotional states of rats observed in the elevated plus maze. These effects seem likely to involve CCKA receptors since they were reversed by the selective CCKA antagonist L364,718 (100 micrograms/kg, 200 micrograms/kg IP) and not observed after injection of 0.1 to 1000 fmol unsulfated cholecystokinin octapeptide (CCK8NS) in the same region. On the other hand, CCK8 or CCK8NS injected into the anterior NAS did not significantly modify these behaviors. These results support the neuroanatomical heterogeneity in the distribution of CCK and its binding sites in the NAS, but raise the question of the presence of CCKA receptors not detected in binding studies and of the behavioral effects mediated by CCKB receptor stimulation in this structure.