Circadian rhythms in blood glucose and the effect of different lighting schedules, hypophysectomy, adrenal medullectomy and starvation

摘要: With other environmental factors rigidly standardized, normal Sprague-Dawley rats were maintained under the following lighting schedules: (1) LD 12:12, artificial light from 6:00 A.M. to P.M. alternating with 12 hours of darkness; (2) DL reversal first schedule; (3) DD, constant and (4) LL. illumination. During each regimen, blood glucose levels determined on separate subgroups 11 18 animals at bi-hourly intervals during a 24-hour period. Significant circadian fluctuations or rhythms all conditions found when mean values for group plotted as function time. Rats 12:12 showed approximately 25% difference between maximum minimum values. When phasing peaks troughs rhythm in was compared that colony Wistar rats, it noted they similar. Starvation 66 did not abolish characteristic rhythm, although lower level resulted. The pattern reversed by reversing cycle 180 degrees. Under LL DD crests seen curves out phase those other; this suggested had become free-running because absence light-dark synchronizer. Hypophysectomy modified but its fluctuating nature; no longer an effective entraining agent. Adrenal medullectomy caused overall 13% decrease alter pattern. significance periodicity analysis relation bioassay is discussed.