Circadian Analysis of Behavior Using Animal Activity Meter and Infrared Thermography in Rats

Abstract

Rats are nocturnal animals that display heightened activity at night and variations in body temperature. Traditionally, behavioral studies have depended on observational methods; however, technological advancements, such as animal activity meters and infrared thermography, now provide more precise and non-invasive evaluations of both behavior and surface temperature measurement. These instruments possess significant potential for enhancing the precision and profundity of behavioral and physiological research. This study examined the exploratory behavior, locomotor activity, and surface temperature of rats during light and dark phases. Ten male Sprague-Dawley rats were kept on an artificial 12-hour dark/12-light cycle. The behavior and body surface temperature were measured twice daily, both during the dark cycle (6 PM) and at light cycle (6 AM). Their activity and behavior, including distance traveled, resting time, ambulatory time, and stereotypic time, were measured using the Optovarimex-Auto Track system. The surface body temperature was measured at four regions (nose, mouth, testis, and abdomen) via an infrared thermal camera. The ambulatory time and distance traveled were statistically significantly higher during the dark cycle compared to during the light cycle. In contrast, the stereotypic time was statistically significantly higher during the light cycle compared to during the dark cycle. Despite the different intensity of activity between photoperiods, there was no significant difference in surface temperature between the dark and cycle. It is concluded that the behavior change in rats during their circadian rhythm can be measured using an animal activity meter.