The pattern of motor activity, light, and melatonin production in Syrian hamsters

To investigate the motor rhythm of the Syrian hamster under natural photoperiod and to relate these findings to pineal rhythm, animals were left undisturbed in metabolic cages in which stabilimeter systems registered motor activity, photovoltaic cells registered light intensity, and in which urinary output was used for the assay of the major melatonin metabolite 6-sulphatoxymelatonin. The motor activity of two animals was monitored during 1 month and showed a striking similarity. Melatonin secretion was measured during 3 consecutive days and showed a night/day ratio in both animals that was relatively constant and that was coupled to the diurnal rhythm of the animals' activity.