BASOLATERAL AMYGDALA LESIONS BLOCK THE MEMORY-ENHANCING EFFECT OF GLUCOCORTICOID ADMINISTRATION IN THE DORSAL HIPPOCAMPUS OF RATS

These experiments examined the effects of bilateral amygdala nuclei le sions on modulation of memory storage induced by bilateral intrahippoc ampal microinfusions of glucocorticoids in male Sprague-Dawley rats. P ost-training infusions of the glucocorticoid receptor (type II) agonis t RU 28362 (3.0 or 10.0 ng) enhanced inhibitory avoidance retention, a nd infusions of the glucocorticoid receptor antagonist RU 38486 (3.0 o r 10.0 ng) administered shortly before training in a water maze spatia l task did not affect acquisition, but impaired retention. In both tas ks, neurochemically induced lesions of the basolateral but not of the central amygdala blocked the memory-modulatory effects of the intrahip pocampal infusions of the drugs affecting glucocorticoid receptors, Le sions of the central amygdala alone impaired inhibitory avoidance rete ntion, but basolateral amygdala lesions alone did not affect acquisiti on or retention in either task. These findings are consistent with pre vious evidence indicating that lesions of the basolateral amygdala blo ck the memory-modulatory effects of systemically administered glucocor ticoids, and provide further evidence that the basolateral amygdala is a critical area involved in regulating glucocorticoid effects in othe r brain regions involved in memory storage.