CORRELATIVE CIRCADIAN-RHYTHMS OF CHOLECYSTOKININ AND DOPAMINE CONTENTIN NUCLEUS-ACCUMBENS AND STRIATUM OF RAT-BRAIN

Due to contrary results concerning the interaction of cholecystokinin and dopamine (CCK/DA) circadian variations in CCK/DA concentration wer e investigated in forebrain nuclei of rats (Nc. accumbens, striatum) i n order to assess the influence of time of day on neurotransmission. C CK was determined by a radioimmunoassay, DA was measured by electroche mical detection after HPLC separation. A distinct circadian rhythm, su perimposed by harmonics (12 h, 6 h) was found in the content of both D A and CCK. A trough was shown for CCK during the light phase and a cre st during the late afternoon and the darkphase, respectively. For DA t he opposite was found. Caused by a phase-shift of about 3-4 h, the CCK /DA rhythms are negatively correlated. The differences are significant at 11.00 h, 13.00 h, 21.00 h, and 03.00 h. The results indicate that circadian processes are involved in neuronal transmission of CCK and D A.