| Research Abstract |
The Djungarian hamster shows daily torpor in winter, and the daily torpor has close relationships to the annual cycles ofbody weight, food intake and so on, and is affected by environmental factors such as photoperiod and temperature. First of all, hamsters were placed on the veranda of the University building to investigate the various physiological parameters under semi-natural condition. The results were summarized in "Annual rhythmicity of the Djungarian hamster under semi-natural outdoor condition." Second of all, we analyzed the roles of photoperiod and temperature in the annual rhythmicity. Since the effects of light and temperature on the annual rhythmicity of body weight, food intake, food storage and pelage color were described previously (Masuda and Oishi, 1988), we investigated the effects on body components and locomotor activity rhythms. The results were described in "Effects of photoperiod and temperature on the body components of Djungarian hamsters", and "Locomotor activity rhythms of the Djungarian hamster under long and short photoperiods." Thirdly, a restricted feeding experiment was performed to clarify the relationship between body weight and food intake. The results were described in "Analysis of the factors involved in photoperiod-induced body weight change by means of restricted feding." We investigated gonadotropins and their receptors and thyroid hormone levels to clarify the endocrinological base for the annual changes of these physiological parameters (Tsutsui et al., 1988, 1989 ; Masuda and Oishi, 1989). We further investigated the effects of these hormones, and the results were described in"Effects of gonads, gonadal hormones, melatonin, and thyroid hormones on the body weight and food intake in the Djungarian hamster." Thus, we were able to obtain data on various physiological parametesr which have close relation to daily torpor.
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