Involvement of NMDA receptors within the amygdala in short- versus long-term memory for fear conditioning as assessed with fear-potentiated startle.
Pretraining intra-amygdala infusions of the NMDA receptor antagonist. D,L-AP5, block fear-potentiated startle in rats tested 24+ hr after training. This may reflect a failure of either acquisition or retention. To evaluate these alternatives, rats were tested for fear-potentiated startle during fear conditioning (30 light-shock pairings [0.6 mA shock]), as well as 1-30 min and 48 hr after fear conditioning. Amygdala lesions abolished fear-potentiated startle at all train-test intervals. Intra-amygdala AP5 infusions (25 nmol/side) abolished fear-potentiated startle during the long-term test and had partial effects at shorter train-test intervals. When the level of fear-potentiated startle during the short-term test was lowered to that of the 48-hr test (i.e., by training rats with a lower, 0.3 mA footshock), AP5 abolished fear-potentiated startle at each timepoint. Thus, amygdala NMDA receptors appear to participate in the initial acquisition of fear memories.
Walker
D L
DL
Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia 30322, USA. dlwalke@emory.edu
Davis
M
M
D000679:Amygdala / Q000502:physiology*; D000818:Animals; D001245:Association Learning / Q000502:physiology; D001931:Brain Mapping; D003214:Conditioning, Classical / Q000502:physiology*; D005239:Fear / Q000502:physiology*; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D013216:Reflex, Startle / Q000502:physiology*; D012153:Retention, Psychology / Q000502:physiology*
D016194:Receptors, N-Methyl-D-Aspartate