Circadian Changes in Synaptic Ribbons in the Pineal Organ of the Japanese Common Newt, Cynops pyrrhogaster pyrrhogaster(Physiology)

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Previous behavioral experiments on the Japanese common newt, Cynops pyrrhogaster pyrrhogaster, have revealed that the pineal organ plays an important role in locomotor activity rhythms. In the present study, morphological changes in the pineal organ were investigated with an electron microscope. In the pineal organ, there are synaptic ribbons surrounded by numerous clear vesicles in the photoreceptor basal process. The number of synaptic ribbons was found to exhibit a daily rhythm, and was low during the light phase and increased to attain a peak during the dark phase under different light conditions. The length of synaptic ribbons also showed the similar daily rhythm, although significant daily changes were not observed under a short photoperiod. The daily rhythm in the number of synaptic ribbons persisted and showed a free running rhythm under con stant darkness. These results suggest that the daily rhythms in the number of synaptic ribbons are endogenous circadian rhythms entrained to a light-dark cycle. Although the exact function of synaptic ribbons in Cynops has not been known, these rhythms might be good indicators for investi gating the rhythmic function of the pineal organ.
社団法人日本動物学会の論文
1985-04-15