Entrainment of the circadian system of the house sparrow: A population of oscillators in pinealectomized birds |
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Authors: | Joseph S Takahashi Michael Menaker |
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Institution: | (1) Institute of Neuroscience, University of Oregon, 97403 Eugene, Oregon, USA;(2) Present address: Section of Pharmacology, Laboratory of Clinical Science, National Institute of Mental Health, Building 10, Room 2D-47, 20205 Bethesda, Maryland, USA |
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Abstract: | Summary Removal of the pineal gland modifies the entrainment behavior of house sparrows. Abnormal entrainment occurs in pinealectomized sparrows exposed to skeleton photoperiods (light cycles composed of 2 pulses of light per 24-h cycle). This abnormal entrainment depends upon the state of the locomotor activity (rhythmic or arrhythmic) before exposure to the light cycle, and upon the interval between the 2 pulses of light which constitute the skeleton photoperiod. The conditions that produce abnormal entrainment in pinealectomized birds are strongly correlated with those that produce 2 stable phases of entrainment to skeleton photoperiods in normal birds ( bistability phenomenon ). These results suggest that after pinealectomy, there remains a population of oscillators whose combined output is reflected in the locomotor activity of individual sparrows.Abbreviations
LD 12
12 light-dark cycle with 12 h of light and 12 h of dark per 24-h cycle
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CT
circadian time |
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