Abstract
It is well known that the lighting conditions affect many physiological phenomenon of laboratory animals. However, lighting conditions are frequently disturbed by investigators themselves. In this study, behavioral (ambulation and drinking) rhythmicities of rats were investigated after irregular lighting; i. e. presentation of short time lightings at 21: 00, 24: 00 and 3: 00 for 12 min during dark period (18: 00-6: 00) . Vaginal smear was taken and sexual cycle was observed everyday. Ambulatory and drinking activities were measured by Gundai type Ambulo-drinkometer. The irregular lightings produced the following changes in the rhythmicities: 1) increase in the ambulatory activity during 15: 00-18: 00 immediately before dark period 2) decrease in ambulatory activity before ovulation 3) disappearance of inhibitory phenomenon of drinking activity which was usually observed before ovulation 4) increase in the drinking activity during 6: 00-9: 00 immediately after dark period 5) the changes in rhythmicities of the behavioral activities lasted for more than 1 month after replacement to the regular lighting condition.
