期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：3
页码：1295-1299
DOI：10.1073/pnas.74.3.1295
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：In alternating 12-hr periods of light and darkness, start of the dark period entrains the hamster's 24-hr clock. Blinding or constant darkness frees the clock of entrainment by allowing it to run faster or slower than 24 hr. Constant light frees the clock from entrainment and permits it to run slower than 24 hr--that is, lengthening its period. Heavy water given in drinking water linearly lengthens the period of the 24-hr clock of blinded hamsters or of hamsters kept in constant darkness in direct proportion to concentration of heavy water (1--50%). Heavy water (1-35%) has very different effects on length of the periods of the 24-hr clock when given under conditions of alternating 12-hr periods of light and darkness. Under these conditions, length of the period is controlled by three factors: (i) heavy water which slows the 24-hr clock; (ii) constant light which also slows the 24-hr clock; (iii) the counteracting effects of entrainment. It is thus possible to observe the effects of all three forces simultaneously in the same animal. The clock slowed by heavy water (1--20%) showed a strong tendency to return to a 24-hr entrainment whenever possible. On a 50% concentration of heavy water, the length of period of the clock became markedly lengthened but very constant and apparently independent of all external and internal disturbances.
