Vasopressin messenger ribonucleic acid in supraoptic and suprachiasmatic nuclei: appearance and circadian regulation during development.

The developmental appearance and regulation of hypothalamic vasopressin (prepropressophysin) mRNA was studied using quantitated in situ hybridization techniques. Vasopressin mRNA levels in the supraoptic nuclei were reliably detected on day 16 of gestation, while mRNA in the suprachiasmatic nuclei (SCN) was detectable on day 21. These developmental patterns correlate well with the immunohistochemical appearance of prepropressophysin translation products previously reported in these nuclei. A prominent day-night rhythm of vasopressin mRNA levels was evident in the SCN on day 21 of gestation; the rhythm was also present on postnatal days 2 and 11. No such rhythm was present in the supraoptic nuclei at any developmental stage examined. These results demonstrate regulated expression of the vasopressin gene during fetal life. Vasopressin mRNA levels in the SCN are already under specific circadian control when the nuclei are morphologically immature and lacking many of the connections found in adult animals.