Abstract:
The circadian rhythm of locomotor activity of the field mouse Musbooduga was studied and single animal phase response curves (PRCs) (n = 8) were constructed for 15-min daylight pulses of 1000 lux intensity. The light pulses, presented at different phases of the circadian cycle, evoked advancing and delaying phase shifts (Delta phi s) depending on the circadian time (CT) of light pulse application. Delta phi s by light pulses applied at the same phase are strongly correlated with the animals' circadian period (tau). The results indicate a significant correlation between (i) tau and the area under the advance zone of the PRC (A) (r = +0.72, p much less than 0.05), (ii) tau and the area under the delay zone of the PRC (D) (r = -0.98,p much less than 0.00001), (iii) tau and the difference between the area under delay and advance zone of PRC (D-A) (r = -0.97, p much less than 0.00001), and (iv) between tau and Delta phi s (at various phases of the circadian cycle) and further suggest that the waveform and time course of PRC depend on the animals' endogenous period (tau).
