Memory enhancement of classical fear conditioning by post-training injections of corticosterone in rats.
There is extensive evidence that post-training administration of the adrenocortical hormone corticosterone facilitates memory consolidation processes in a variety of contextual and spatial-dependent learning situations. The present experiments examine whether corticosterone can modulate memory of auditory-cue classical fear conditioning, a learning task that is not contingent on contextual or spatial representations. Male Sprague-Dawley rats received three pairings of a single-frequency auditory stimulus and footshock, followed immediately by a post-training subcutaneous injection of either corticosterone (1.0 or 3.0mg/kg) or vehicle. Retention was tested 24h later in a novel test chamber and suppression of ongoing motor behavior served as the measure of conditioned fear. Corticosterone dose-dependently facilitated suppression of motor activity during the 10-s presentation of the auditory cue. As corticosterone administration did not alter responding after unpaired presentations of tone and shock, tone alone, shock alone or absence of tone/shock, the findings indicated that corticosterone selectively facilitated memory of the tone-shock association. Furthermore, injections of corticosterone given 3h after training did not alter motor activity during retention testing, demonstrating that corticosterone enhanced time-dependent memory consolidation processes. These findings provide evidence that corticosterone modulates the consolidation of memory for auditory-cue classical fear conditioning and are consistent with a wealth of data indicating that glucocorticoids can modulate a wide variety of emotionally influenced memories.
Hui
Gabriel K
GK
Center for the Neurobiology of Learning and Memory, Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-3800, USA.
Figueroa
Isabel R
IR
Poytress
Bonnie S
BS
Roozendaal
Benno
B
McGaugh
James L
JL
Weinberger
Norman M
NM
D000818:Animals; D001143:Arousal / Q000187:drug effects; D001245:Association Learning / Q000187:drug effects*; D001307:Auditory Perception / Q000187:drug effects; D003214:Conditioning, Classical / Q000187:drug effects*; D003345:Corticosterone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005239:Fear / Q000187:drug effects*; D006624:Hippocampus / Q000187:drug effects; D007279:Injections, Subcutaneous; D008297:Male; D011939:Mental Recall / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012153:Retention, Psychology / Q000187:drug effects*
D003345:Corticosterone