Functional Morphology of the Suprachiasmatic Nucleus with Special Reference to its Role as the Circadian Oscillator Under Influence of Retinal Input.

1990 Fiscal Year Final Research Report Summary

• Project/Area Number: 01480112
• Research Category: Grant-in-Aid for General Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: 神経解剖学
• Research Institution: Kyoto Prefectural University of Medicine
• Principal Investigator: IBATA Yasuhiko Kyoto Pref. Univ. Med., Dept. Anat., Professor., 医学部, 教授 (10079684)
• Co-Investigator(Kenkyū-buntansha): ICHITANI Yukio Kyoto Pref. Univ. Med., Dept. Anat., Associate, 医学部, 助手 (80176289) ; TAKAGI Shin Nagoya Univ., Faculty of Science, Assosiate, 理学部, 助手 (90171420) ; FUKUI Kenji Kyoto Pref. Univ. Med., Dept. Psychiat., Assistant Prof., 医学部, 講師 (50165263) ; OKAMURA Hitoshi Kyoto Pref. Univ. Med., Dept. Anat., Assosiate Prof., 医学部, 助教授 (60158813)
• Project Period (FY): 1989 – 1990
• Keywords: suprachiasmatic nucleus / VIP / vasopressin / mRNA / immunocytochemistry / in sity hybridization / retina / primate

Research Abstract

The aim of this project is to clarify the functional roles of the suprachiasmatic nucleus (SCN) as the oscillator of several physiological behaviors by immunocytochemistry and in situ hybridization techniques. The following results were obtained.
1. VIP neuronal elements whose neuronal perikarya are distributed in the ventral portion of the SCN demonstrated diurnal variation of their immunoreactivity against VIP antiserum by immunocytochemistry and color image analysis. Most intensive VIP immunoreactivity was observed in the animals sacrificed at 0200h and weakest at 1400h.
2. The messenger RNA (mRNA) of VIP in the SCN also showed diurnal alteration by in situ hybridization using cDNA of VIP probe and computer analysis. Amounts of VIP mRNA became to be largest at 0200h and to the smallest at 1400h. However as compared with immunoreactivity we confirmed that the onset of fluctuation of mRNA occurred 2-6h prior to diurnal variation of the content of VIP-like immunoreactivity. These finding s suggest the light stimulus from the retina is a primarily influence on the transcription of VIP mRNA and induce a diurnal variation of VIP synthesis.
3. Influence of retinal input upon VIP neuronal elements both in the SCN and the superior colliculus was examined by immunocytochemistry after eye enuleation. The contrary effects were observed in VIP neuronal elements between the SCN and the superior colliculus. Immunoreactivity of neuronal elements particularly their fibers and terminals in the SCN remarkably increased after eye enucleation, while their immunoreactivity decreased in the superior colliculus.
4. The possibility of direct neuronal inputs of VIP neurons upon vasopressin neurons in the SCN was suggested by double labeling immunoelectron microscopy using antisera against VIP and vasopressin.
5. VIP and vasopressin immunoreactive elements in the SCN of the Japanese monkey (Macaca fuscata) was studied by light and electron microscopic immunocytochemistry since almost of morphological and physiological investigations of the SCN have been carried out using the rodent as the material. In this study VIP immunoreactive neurons are considered at least to play a role as the intrinsic neurons in the SCN.