A long-term stress exposure impairs maze learning performance in rats.

To elucidate hippocampal dysfunctions following chronic stress exposure, we evaluated the effect of chronic stress on maze learning performance, as assessed by a radial eight-arm maze task. In the 12-week stress sessions, male rats in the stress group were exposed to the stress of a 15-min immersion in cold water once a day and, rats in the control group were slightly handled. Rats in the stress group performed significantly poorly during the acquisition period (P < 0.01) and required more trials to attain at least seven correct choices in the first eight choices for five consecutive trials (P < 0.05). Together with our previous findings that chronic stress exposure damages the hippocampus histologically, we concluded that chronic stress exposure resulted in an impairment of maze learning performance, probably due to hippocampal damages.