CIRCADIAN-RHYTHMS IN THE RELEASE OF VASOACTIVE INTESTINAL POLYPEPTIDEAND ARGININE-VASOPRESSIN IN ORGANOTYPIC SLICE CULTURE OF RAT SUPRACHIASMATIC NUCLEUS

Temporal profiles of the amount of vasoactive intestinal polypeptide ( VIP) were examined in the medium of organotypic suprachiasmatic nucleu s (SCN) slice cultures over a 2-day period. Arginine-vasopressin (AVP) level was also measured in the same medium. The slices of the SCN wer e obtained from 7-8-day-old rats and cultured individually in tubes on a roller drum for 14 days. The VIP amount in the medium of SCN cultur e showed a circadian rhythm with a similar to 22-h period. Circadian r hythms with identical periods were also observed in AVP amount of the same culture. However, the peak time of the VIP rhythm was slightly ah ead of that of the AVP rhythm. Furthermore, the total VIP amount in th e medium over a 24-h period was six times as large as that of AVP. The se results suggest that there is a circadian rhythm of VIP which is re leased from the ventrolateral SCN.