Vasoactive intestinal peptide immunoreactive neurons in the rat suprachiasmatic nucleus demonstrate diurnal variation.
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.
Takahashi
Y
Y
Department of Ophthalmology, Kyoto Prefectural University of Medicine, Japan.
Okamura
H
H
Yanaihara
N
N
Hamada
S
S
Fujita
S
S
Ibata
Y
Y
D000818:Animals; D002940:Circadian Rhythm; D007124:Immunoenzyme Techniques; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000032:analysis*
D014660:Vasoactive Intestinal Peptide