Microinjection of morphine into the nucleus accumbens impairs contextual learning in rats.
A unilateral microinjection of morphine into the amygdala impaired fear conditioning to both a conditioned stimulus (CS) paired with shock and the context where shock occurred, whereas a microinjection of morphine into the nucleus accumbens (NA) spared fear conditioning to the CS but impaired, in a dose-dependent and receptor-specific manner, fear conditioning to the context. Morphine in the NA also spared extinction and latent inhibition of a CS but abolished the context specificity of these effects and eliminated the increase in discriminability that results from preexposure to a to-be-shocked context. The results identify a role for the NA in the processes by which rats learn about a context and are discussed in terms of an opioid disruption of either within-context associations or of attentional processes that contribute to such associations.
Westbrook
R F
RF
School of Psychology, University of New South Wales, Sydney, Australia. f.westbrook@unsw.edu.au
Good
A J
AJ
Kiernan
M J
MJ
D000818:Animals; D001245:Association Learning / Q000187:drug effects*; D001931:Brain Mapping; D003214:Conditioning, Classical / Q000187:drug effects*; D004597:Electroshock; D005239:Fear / Q000187:drug effects*; D008297:Male; D011939:Mental Recall / Q000187:drug effects; D008845:Microinjections; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D009714:Nucleus Accumbens / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012931:Social Environment
D009270:Naloxone; D009020:Morphine