Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2012697 | Pharmacology Biochemistry and Behavior | 2015 | 8 Pages |
Abstract
While not well understood, the NMDA (N-methyl-D-aspartate) antagonist ketamine, a dissociative anesthetic, has been reported to be efficacious in depression and related psychological disorders. Conditioned fear is a normal emotional conditioning process that is known to become dysfunctional in individuals suffering from Post-Traumatic Stress Disorder (PTSD) and related stress disorders. We examined the effects of ketamine to determine the potential modulation of the acquisition and extinction of a conditioned fear using a conditioned suppression procedure. Rats were trained on a variable interval (VI), food maintained, operant conditioning task to establish a general measure of performance. Rats were exposed to inescapable shock (IES, unconditioned stimulus) paired (ÃÂ 20) with an audio/visual conditioned stimulus (CS) to establish conditioning. Conditioning was quantified by measuring response suppression following CS presentation during subsequent extinction trials where the CS alone was presented. Ketamine or vehicle was administered either after initial conditioning or after each of the subsequent extinction trials. For each regimen, a series of four injections were administered 60Â min apart (100, 50, 50, 50Â mg/kg, respectively) in order to sustain a ketamine effect for a minimum of 4Â h. Ketamine produced a general decrease in responding on the VI, relative to baseline, as response rates were slower on the operant task when tested 24Â h later and longer. Ketamine did not affect the acquisition of the conditioned fear when the regimen was administered shortly after the initial pairings of IES and CS. Ketamine did not alter extinction to the conditioned fear when the regimen was administered following each CS only presentation following initial conditioning. Our conclusion from these findings is that while ketamine alters behavior on an appetitively motivated operant task it does not, however, appear to directly modulate learning and memory processes associated with conditioned fear.
Related Topics
Life Sciences
Biochemistry, Genetics and Molecular Biology
Biochemistry
Authors
Caitlin M. Groeber Travis, Daniel E. Altman, Raymond F. Genovese,