ACUTE STRESS, BUT NOT CORTICOSTERONE, FACILITATES ACQUISITION OF PAIRED ASSOCIATES LEARNING ASSESSED IN RATS USING TOUCHSCREEN-EQUIPPED OPERANT CONDITIONING CHAMBERS

Abstract

Acute stress is well known to influence learning and memory tasks in humans and rodents, enhancing performance in some instances while impairing it in others. Across species, subjects preferentially employ striatal mediated stimulus-response strategies in spatial memory tasks following stress, making use of fewer hippocampal based strategies which are thought to be more cognitively demanding. Previous research has demonstrated that the acquisition of rodent paired associates learning (PAL) relies primarily on the striatum, while later task performance can be impaired through hippocampal disruption. Therefore, we sought to explore whether the acquisition of this task could be enhanced by acute stress. Male Long-Evans rats were trained to a predefined criterion in PAL and were subjected to either a single session of restraint stress (30 min) or injection of corticosterone (CORT; 3 mg/kg). Daily performance was then monitored for one week. We found that only the animals subjected to restraint stress performed with higher accuracy and task efficiency, when compared to untreated controls. These results suggest that while acute stress enhances the acquisition of PAL, CORT alone does not. This may be due to differences which have been identified between these treatments and their ability to produce sufficient catecholamine release in the amygdala, a requirement for stress effects on memory. However, as the effect of restraint stress was moderate and not significantly improved over CORT, these results should be interpreted with caution until these findings are replicated.