Takahashi Y, Okamura H, Yanaihara N, Hamada S, Fujita S, Ibata Y
Department of Ophthalmology, Kyoto Prefectural University of Medicine, Japan.
Brain Res. 1989 Sep 18;497(2):374-7. doi: 10.1016/0006-8993(89)90283-7.
The suprachiasmatic nucleus (SCN) of mammals is considered to be a circadian oscillator and it also demonstrates circadian rhythmicity of its multiple unit activity. A number of neuropeptides have been found in the SCN. Vasoactive intestinal peptide (VIP)- and vasopressin-containing neurons comprise large populations of these cells and have a distinct distribution within the nucleus. Therefore we attempted to examine whether the VIP neurons show a diurnal alteration of their immunoreactivity by combined immunocytochemistry and color image analysis. Our results demonstrate that VIP-like immunoreactive neurons show a diurnal change in the amount of immunoreactivity. Immunoreactivity was most intense in the sections from rats maintained in the cyclic photoperiod and sacrificed at 02.00 h and weakest in the SCN from animals sacrificed at 14.00 h. We considered that VIP-like immunoreactive neurons showed diurnal variation of VIP synthesis depending strongly on the light from the retina.
