Light-induced phase response curves of the circadian activity rhythm in individual field mice, Mus booduga.

Abstract

The circadian rhythm of locomotor activity of the field mouse Mus booduga 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 < 0.05), (ii) tau and the area under the delay zone of the PRC (D) (r = -0.98, p < 0.00001), (iii) tau and the difference between the area under delay and advance zone of PRC (D-A) (r = -0.97, p < 0.0001), 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).