Circadian differences between two rat strains in their feeding and drinking micro- and macrostructures.

Basal divergences in circadian feeding and drinking patterns among different rat strains may bias comparative physiological and pharmacological studies. To examine this issue in detail, Long-Evans (Turku/AB) (L-E) and Han/Wistar (Kuopio) (H/W) rats were monitored with an automated system for seven consecutive days after a habituation period. For the analysis, days were split into hours or into four diurnal periods, and the chronologically repetitive nature of the data was taken into account. While L-E rats displayed two distinct peaks in feeding and drinking that coincided with the light shifts, H/W rats exhibited their lowest consummatory activity at the morning light shift. Further differences were recorded in a number of variables including numbers of meals and drinking episodes as well as their durations. These findings reveal surprisingly wide inter-strain differences. Hence, one should be careful in generalizing ingestive behavioural data obtained from a single rat strain to the entire species. [ABSTRACT FROM AUTHOR]