An Assessment of Changes in Open-Field and Elevated Plus-Maze Behavior Following Heat Stress in Rats

This paper presents the effect of high environmental heat on behavior of the male Charles Foster rats. Eighty rats were divided into three groups, subjected to (i) acute heat stress (ii) chronic heat stress and (iii) handling control group. Animals were exposed to the hot environment in a biological oxygen demand incubator at 38 ± 1ºC (relative humidity 45-50%) for four hours of continuous single exposure for acute heat stress and one hour daily for 21 days for chronic stress. The assessment of behavior was performed just after the stress for acute stress group and for chronic stress group, on 1st, 7th, 14th and 21st day of stress in open-field (OF) and Elevated plus-maze (EPM) apparatus. Following acute heat exposure, a significant increase in immobilization with decrease in rearing, grooming, and ambulation behavior was seen in OF. While in EPM, a highly significant increase in transfer latency with decrease in percentage time on open arms and number of arms crossed were recorded. During chronic heat stress, in OF, decrease in immobilization (1st, 7th and 14th day) and ambulation (1st and 7th day) was observed with significant increase in rearing (1st day) and grooming behavior (1st and 7th day). On the other hand, in EPM, significant decreases in number of arms crossed (1st, 7th and 14th day) and transfer latency (1st day) were recorded with increase in percentage time on open arms (1st and 7th day). However, no behavioral changes were observed on 21st day that show the adaptations of animals to the chronic exposure to the hot environmental conditions