ADMINISTRATION OF CHOLECYSTOKININ SULFATED OCTAPEPTIDE (CCK-8S) INDUCES CHANGES ON RAT AMINO-ACID TISSUE-LEVELS AND ON A BEHAVIORAL-TEST FOR ANXIETY

1. The effect of the intraperitoneal administration of cholecystokinin sulphated octa peptide (CCK 8S) (10 nmol/kg i.p.) on endogenous level s of several amino acids in five areas of the rat brain was analyzed. The olfactory bulb, hypothalamus, hippocampus, cerebral frontal cortex , and corpus striatum were evaluated. In addition, the effects of CCK- 8S and PD 135,158 (1 mg/kg), a selective CCKB antagonist, on the perfo rmance of rats submitted to a dark/light transition test were also stu died. 2. Upon administration of CCK-8S, the concentration of glutamate was reduced (27%) in the olfactory bulb. The same was observed when t he levels of glycine (31%) or alanine (43%) were determined. No signif icant effects were produced by CCK-8S on cortical and hypothalamic lev els. In the hippocampus, the concentration of both glutamate (27%) and taurine (29%) were reduced, whereas the levels of GABA in the striatu m (29%) were increased. 3. After a single injection of CCK-8S, the tim e spent by the rats in the illuminated site of the dark/light transiti on test box, was not changed. On the contrary, the administration of P D 135,158 increased the time spent in the lighted compartment. 4. Thes e results show that systemic administration of CCK 8S produced regiona l specific changes in brain amino acids, without producing any signifi cant behavioral modification in the rat exposed to a dark/light box. I n contrast, the selective CCKB receptor antagonist, PD 135,158, induce s anxiolytic-like action in an animal model of anxiety. (C) 1998 Elsev ier Science Inc.