Study on the pathophysiological mechanism of the sleep-wake rhythm disorder caused by the phase change of LD cycle.

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The aim of this study was to clarify the pathophysiological mechanisms of sleep-wake rhythm dysfunction in "jet-lag" syndrome. I have recorded rats' vigilance state, body temperature (Tb), blood pressure (BP) and heart rate (HR) simultaneously for about 2 weeks, and done the following studies : 1) the observation of the diurnal rhythm in each parameter and its interaction under the ordinary 12-12 hours light-dark (LD) cycle ; 2) the observation of the change of the diurnal rhythm in each parameter and its interaction under an 8-hour LD cycle phase advance ; 3) the observation of effect of vitamin B12 on the change of diurnal rhythm obtained in 2). As a result, 1) although HR and Tb showed a similar sinusoidal diurnal variation in all vigilance states, the diurnal profile for the BP was dependent on vigilance state. During wake (W), the BP diurnal variation was higher during the dark phase, during NREM sleep (NREMS), no significant diurnal change was seen, while during REMS,the BP exhib … More ited reversed diurnal variation, i.e., it was higher during the light phase than the dark phase. The phasic fluctuation of BP during REMS was greater in the light phase than the dark phase ; 2) phase advance of the LD cycle led to an increase in both NREMS and REMS.Although the circadian amplitude of NREMS decreased just after the phase advance, that of REMS temporarily increased, and REMS diurnal pattern hardly changed for 4-5 days after phase advance. The amount of NREMS in the light period correlated positively with that in the preceding dark period for 4-5 days after phase advance, indicating that homeostatic control of the amount of NREMS was disturbed by phase advance. The circadian amplitude of Tb also decreased from just after phase advance. There was no large change in the diurnal rhythm of BP and HR in all vigilance state ; 3) continuous intraperitoneal infusion of vitamin B12 by an osmotic pump suppressed the increase of sleep after the phase advance of LD cycle. Vitamin B12 can be effective in prevention of the "jet-lag" syndrome. Less