MODULATION OF STRIATAL ASPARTATE AND DYNORPHIN-B RELEASE BY CHOLECYSTOKININ (CCK-8) STUDIED IN-VIVO WITH MICRODIALYSIS

SULPHATED cholecystokinin-8 (CCK-8) given into the neostriatum of the rat by in vivo microdialysis produced a concentration-dependent (1-100 mu M) increase in extracellular aspartate (Asp) and dynorphin B (Dyn B), but not in glutamate, GABA or dopamine levels. The increase in Asp levels produced by 10 mu M CCK-8 was similar to 10 fold and was inhibited (similar to 50%) by the CCKB antagonist L-365,260 (20 mg kg(-1) i.p.), while the increase in Dyn B (similar to 2 fold) was totally abolished. Both increases were inhibited (similar to 50%) by local infusion of 10 mu M of tetrodotoxin (TTX). Thus, CCK exerts modulatory effects in the basal ganglia, possibly by interacting with local neostriatal neurones releasing Asp, and with Dyn B-containing neurones projecting to the pars reticulata of the substantia nigra.