International Joint Research on Pineal Photoereception

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Environmental photic information regulates the function of pineal organs. In order to elucidate basic mechanisms of pineal functions, the international and interdisciplinary cooperative research was undertaken between our laboratory and the scientists from Germany, U.S.A., New Zealand and India. Main findings are as follows.1. Electrophysiological and immunocytochemical study of pineal organs and retina of the Antarctic fishes, Pagothenia and Trematomus, Showed that they are well-developed photosensitive organs.2. UV-receptor was found electrophysiologically in the lamprey's pineal, showing the peak sensitivity at 380 nm.3. Application of NADPH-diaphorase staining demonstrated 4 types of pineal neurons, which could be subdivided into 8 groups. Double immunostaining with antisera against seretonin and rod-opsin was successful. A new cell-type with rob-opsin positivity without processes was found. Cone-opsin immunoreactivity suggested the presence of deep-brain photoreceptors in the paraventricular organ of lamprey.4. Amazonian electric fish had pineal organs. In the retina of electric eel, rod-opsin immunoreactivity was shown in outer segments of visual cells, but no serotonin-positive amacrine cells were demonstrated.5. Pineal photoreceptors of the lamprey were studied electrophysiologically whether they are sensitive to magnetic field.Intracellular recording revealed no change in the resting membrane potential and in photic responses.