Glucocorticoid Effects on Learning, Memory, and CRF




Schmidt, Kevin

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Glucocorticoids are naturally circulating stress hormones that are also commonly synthesized and administered for medical treatments. Corticosterone (CORT) is the primary rat glucocorticoid and recent research has shown that treatments with this steroid can have both beneficial and detrimental effects on learning- and memory-related behaviors, brain structures, and the corticotropic releasing factor (CRF) chemical system. The present experiment administered CORT injections twice daily in rats on postnatal days 15-17 at three different doses: 0.04 mg/g CORT, 0.02 mg/g CORT, and 0.005 ml/g oil vehicle alone. Animals were tested on trace fear conditioning on postnatal day 28, extinction on day 29, and extinction recall on day 30. All animals conditioned and extinguished but there were no significant differences between groups. An in situ hybridization assay found that 0.02 mg/g CORT caused significant elevation in CRF mRNA expression in the infralimbic (IL) cortical region compared to control and 0.04 mg/g CORT while the lateral amygdala was not affected. Thus, CORT has in inverted-u relationship on CRH mRNA regulation in the IL but not the LA and is not correlated with the acquisition of trace fear conditioning.



Glucocorticoids, Learning, Memory, Corticotropic releasing factor, CRF, Rats