Differential effects of transient constant light-dark conditions on daily rhythms ofPeriodandClocktranscripts during Senegalese sole metamorphosis

The flight activity of Culiseta incidens was automatically recorded in constant darkness and constant light after entrainment to light:dark 12:12 to determine the usefulness of a formal circadian pacemaker model in which the periods of two oscillators respond reciprocally to light intensity. Period at activity onset lengthened approximately 0.4 h from darkness to 0.1 lx, whereas period at offset shortened approximately 0.4 h. Thus within this range, the onset of the nocturnal active phase obeyed Aschoff's rule for nocturnal animals, and the offset (or onset of diurnal rest phase) obeyed the rule for diurnal animals. These data supported a model in which, as light intensity increases, the period of one oscillator (evening) increases while that of another (morning) decreases. This model, with additional assumptions, also provided a framework for mutually consistent explanations of other features among the data. These included long periods at 3.5 lx, short periods at 35 lx, a progressively earlier occurrence of inactivity with increasing light intensity, and a clear example of circa-bi-dian (approximately 2 days) rhythmicity.

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Circadian properties of vasopressin and melatonin rhythms in cat cerebrospinal fluid

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1982.243.6.e489 ◽

1982 ◽

Vol 243 (6) ◽

pp. E489-E498 ◽

Cited By ~ 3

Author(s):

S. M. Reppert ◽

R. J. Coleman ◽

H. W. Heath ◽

H. T. Keutmann

Keyword(s):

Cerebrospinal Fluid ◽

Drinking Behavior ◽

Constant Light ◽

Daily Rhythms ◽

Dark Cycle ◽

Melatonin Rhythm ◽

Lighting Conditions ◽

Cycle Lengths ◽

Freely Moving ◽

Freely Moving Cats

Using a method for continuous removal of cisternal cerebrospinal fluid (CSF) from freely moving cats, we delineated the circadian nature of the daily rhythm in CSF arginine vasopressin. The daily melatonin rhythm was also monitored in CSF as another marker of circadian function. Under diurnal lighting conditions, both hormones exhibited prominent daily rhythms; the CSF vasopressin rhythm was characterized by high daytime values, whereas the CSF melatonin rhythm was characterized by high nighttime levels. In contrast, drinking behavior exhibited a 24-h component in only one of four animals studied. Daily CSF rhythms of vasopressin and melatonin persisted for over 78 days of study in constant light. The vasopressin rhythm clearly free-ran in this environment, manifesting cycle lengths of slightly greater than 24 h. The daily melatonin pattern split into several components with increasing time in constant light. An acute 8-h phase delay in the daily light-dark cycle resulted in corresponding but gradual phase shifts in both rhythms. These results indicate that both the vasopressin and melatonin rhythms in cat CSF are endogenously generated and are entrained by the daily light-dark cycle.

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