Locomotor activity patterns of domestic cat (Felis silvestris catus) modulated by different light/dark cycles

The aim of this study was to investigate the influence of different photoperiod schedules on daily total locomotor activity in cat. Four male cats (4 ± 0.3 kg) were housed individually under controlled temperature during the study and were subjected to four different artificial lighting regimes including 12L:12D (light on at 08:00, light off at 20:00), 12D:12L (light on at 20:00, light off at 08:00), 24L:0D (light on for all experimental period), 0L:24D (constant darkness). The application of the statistical analysis of cosinor indicated the existence of a significant daily rhythm (P < 0.05). In particular, in 12L:12D conditions, the cats were more active during the dark phase compared to the light phase, with a range of variation between 23:30 and 24:30 h. During the 12D:12L cycle, all cats changed their locomotor activity rhythm, so that it coincided with the new phase of the photoperiod. The resynchronization to a new LD cycle was quick. Endogenous rhythms were manifested in all cats with different clarity when subjected to 24L:0D cycles. When the cats were exposed to constant darkness, the endogenous periodicity was not observed. These results suggest the existence of an endogenous circadian oscillator that controls the expression of locomotor activity rhythms in the cat.