Selective impairment of long-term but not short-term conditional fear by the N-methyl-D-aspartate antagonist APV.
Previous research has indicated that the competitive N-methyl-D-aspartate (NMDA) antagonist APV (DL-2-amino-5-phosphonovalerate) prevents the Pavlovian conditioning of fear to contextual stimuli when tested 24 hr, but not immediately, after training. The present study investigated this differential time-dependent effect of APV on fear conditioning. Rats were given either APV or saline and presented with 3 footshocks in a distinctive chamber. Promptly after the shock, rats that had received APV exhibited a species-typical fear response-freezing. However, the freezing lasted for only a short period of time (less than 3 min) compared with that of controls. An immediate-shock procedure showed that freezing was entirely a conditional response to the chamber. In addition, the results of a savings test suggest that APV impairs storage rather than retrieval processes. These results indicate that there are two temporally distinct associative fear processes, a short-term NMDA-independent conditional fear and a long-term NMDA-dependent conditional fear.
Kim
J J
JJ
Department of Psychology, University of California, Los Angeles 90024.
Fanselow
M S
MS
DeCola
J P
JP
Landeira-Fernandez
J
J
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology*; D000679:Amygdala / Q000187:drug effects*; D000818:Animals; D001245:Association Learning / Q000187:drug effects; D001931:Brain Mapping; D003214:Conditioning, Classical / Q000187:drug effects*; D004597:Electroshock; D005239:Fear / Q000187:drug effects*; D005260:Female; D011939:Mental Recall / Q000187:drug effects*; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects*; D012153:Retention, Psychology / Q000187:drug effects
D016194:Receptors, N-Methyl-D-Aspartate; D015763:2-Amino-5-phosphonovalerate