Differential effects of selective opioid peptide antagonists on the acquisition of pavlovian fear conditioning. Peptides 1991;12(5):1033-7
Date
09/01/1991Pubmed ID
1686930DOI
10.1016/0196-9781(91)90056-uScopus ID
2-s2.0-0026093964 (requires institutional sign-in at Scopus site) 48 CitationsAbstract
Pretreatment with opioid antagonists enhances acquisition of Pavlovian fear conditioning. The present experiments attempted to characterize the type of opioid receptor responsible for this effect using a procedure that assessed the fear of rats to a chamber previously associated with electric shock (1 mA, 0.75 s). Freezing, a species-typical immobility, was employed as an index of fear. Two mu opioid antagonists, CTOP (40 ng) and naloxonazine (10 micrograms), enhanced conditioning. On the other hand, the kappa antagonist nor-binaltorphimine reduced conditioning. Two delta antagonist treatments (16-methyl cyprenorphine and naltrindole) had no reliable effect on acquisition. Thus the enhancement of conditioning appears to be mediated by mu receptors. Previous research has shown that the conditional fear produced by these procedures caused an analgesia that is also mediated by mu receptors. It is argued that the enhancement effect occurs because of an antagonism of this analgesia and that the analgesia normally acts to regulate the level of fear conditioning.
Author List
Fanselow MS, Kim JJ, Young SL, Calcagnetti DJ, DeCola JP, Helmstetter FJ, Landeira-Fernandez JAuthor
Fred Helmstetter PhD Professor in the Psychology / Neuroscience department at University of Wisconsin - MilwaukeeMESH terms used to index this publication - Major topics in bold
AnimalsConditioning, Classical
Fear
Female
Indoles
Morphinans
Naloxone
Naltrexone
Narcotic Antagonists
Rats
Receptors, Opioid
Receptors, Opioid, delta
Receptors, Opioid, mu
Reference Values
Somatostatin