Chronobiotic effect of melatonin following phase shift of light/dark cycles in the field mouse Mus booduga.

The objective of this study was to assess whether melatonin accelerates the reentrainment of locomotor activity after 6 h of advance and delay phase shifts following exposure to LD 12:12 cycle (simulating jet-lag/shift work). An experimental group of adult male field mice Mus booduga were subjected to melatonin (1 mg/kg) through i.p. and the control group were treated with 50 % DMSO. The injections were administered on three consecutive days following 6h of phase advance and delay, at the expected time of "lights off'. The results show that melatonin accelerates the re-entrainment after phase advance (29%) when compared with control mice. In the 6 h phase delay study, the experimental mice (melatonin administered) take more cycles for re-entrainment (51%) than the control. Further, the results suggest that though melatonin may be useful for the treatment of jet-lag caused by eastward flight (phase advance) it may not be useful for westward flight (phase delay) jet-lag.

Diazepam phase shifts the circadian clock of the field mouse Mus booduga.

Single 2h administration of diazepam (benzodiazepine) in 3·5% ethanol solution was found to evoke advance and delay phase shifts in the locomotor activity rhythm in the field mouse Mus booduga. Through such pulsed administration of diazepam at various phases of circadian rhythm a phase response curve could be constructed. Phase advance occurred during early subjective day (CT 2) and phase delays were observed in the remaining phases. The shape of the diazepam phase response curve is similar to the general shape of the phase response curves generated by intraperitoneal injections of other benzodiazepines in hamsters. The phase shifting action of diazepam may be explained by its agonistic action on the neurotransmitter gamma-aminobutyric acid.

Direct correlation between the circadian sleep-wakefulness rhythm and time estimation in humans under social and temporal isolation.

Several bodily functions in humans vary on a 24 h pattern and most of these variations persist with a circadian period of ca 25 h when subjects are studied under conditions of social and temporal isolation. We report in this paper that the estimates of short time intervals (TE) of 2 h are strongly coupled to the circadian rhythm in sleepwakefulness. There is a linear correlation between the number of hours humans stay awake (α) and their estimation of 2 h intervals. The coupling of TE to α appears to obtain only under conditions of physical well-being.