Differential activation of hippocampus and amygdala following spatial learning under stress.

We examined the activation of memory-related processes in the hippocampus and the amygdala following spatial learning under stress, in the rat. Animals were trained in a water maze in a massed spatial task under two stress conditions (cold and warm water). In the dorsal CA1, training was accompanied by increased phosphorylation of ERK2 only in animals that have acquired the task (irrespective of whether they were trained in cold or warm water). In the amygdala, significant activation of ERK2 was found only in animals that learned the task well under high levels of stress. Hence, the results suggest that the amygdala and the hippocampus are differentially activated following spatial learning, depending on the level of stress involved.