In vivo release of cholecystokinin-like immunoreactivity in rat frontal cortex under freely moving conditions.

Release of cholecystokinin-like immunoreactivity (CCK-LI) was measured in rat medial prefrontal cortex in vivo by brain dialysis and enzyme immunoassay under freely moving condition. Perfusion of 50 mM K+ resulted in the increase of CCK-LI in the dialysate. The data on high-performance liquid chromatography (HPLC) of the dialysate showed that the increase of the CCK-LI was mainly due to the increase of CCK octapeptide sulfate itself. In the preliminary experiments, we applied this brain dialysis method for determination of CCK-LI release with drug treatment. After treatment with sulpiride (i.p.), a D2 dopamine receptor antagonist, a significant increase of CCK-LI was observed, indicating that this brain dialysis technique is applicable to detect change in the level of CCK-LI release after a certain drug treatment.