Tau and phase response curves for non-photic stimuli in blinded rats

Although light is the principal Zeitgeber in mammals, non-photic stimuli have also been described as affecting the properties of a circadian pacemaker. In the present experiment we tested the effect of 4 types of non-photic stimuli (heat and cold pulses, dexamethasone injection and access to a running-wheel) on the circadian rhythm of the motor activity of blinded Wistar rats. The Phase Response Curve and the Tau Response Curve for each stimulus were obtained. Our results show no clear effect of non-photic stimuli on the circadian rhythm of the rat, and thus, question the capacity of these animals to respond to single pulses other than light, and consequently the importance of these type of stimuli in this species.