Die Tagesperiodik des neuro‐hypophysären Adiuretins männlicher Ratten unter Dauerlicht∗∗

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Abstract
Male Wistar rats (Wistar AF/Han.) were kept from birth until the end of the second month alive under constant environmental conditions and an alternating light ‐ dark regimen consisting of 12 hrs light (7.00 ‐ 19.00 hr) and 12 hrs darkness (19.00 ‐ 7.00 hr). At the end of the second month alive the animals were exposed to continuous illumination (about 200 lux) for 4 weeks. The rats were decapitated at 6 different times of the 24‐hr period. The heads were frozen in liquid nitrogen. After excision of the posterior pituitary lobes acetic acid extracts were made and tested for their antidiuretic activity using aethanol ‐ anesthetized male rats as test animals. The results were compared to those obtained in earlier experiments, when male rats had been kept under a rhythmic light‐dark regimen until death. The circadian rhythm of the neurohypophyseal ADH, which had been shown to exist in L/D rats persisted after a 4 weeks’ period of constant light. In comparison to the results with L/D rats the phases of the circadian ADH rhythm in L/L rats had shifted and the amplitudes of the periods were lowered.