Abstract
It has thought that the central information processing of spatial memory using Morris water maze in rodent is hippocampal-dependent paradigm. Recent studies have shown that various types of stressors influence on the rat cognitive function. Especially, a kind of adrenocortical steroid hormone glucocorticoid secreted by activation of hypothalamo-pitituitary-adrenal (HPA) axis has been studied on learning and memory. Animals given immobilization stress prior to training trial had no effects on subsequent learning acquisition and retention test, whereas there was significant effect on impairment of rats, memory retrieval if they were subjected to the stress before retention test. Here we investigated whether foot shock stress (eighty times, 0.5mA for 5s with a 10s intershock interval) would also impair rats, spatial memory retrieval. Furthermore, we measured plasma corticosterone concentration in different timing of following the stress and assessed the relevance between the circulating corticosterone levels and the spatial memory retrieval. The foot shock stress immediately before the retention test significantly impaired the memory retrieval compared to other groups in which given the stress at some different timings. Plasma corticosterone concentration was elevated 20min after the stress in this experiment. These data suggest that memory retrieval, but not learning acquisition, deficit has relevance to the stress intensity and timing and circulating corticosterone levels. [J Physiol Sci. 2006;56 Suppl:S206]
