title: Opioid receptors regulate retrieval of infant fear memories: effects of naloxone on infantile amnesia.
abstract: The authors examined the role of the endogenous opioid system in infantile amnesia for contextual fear conditioning. Rats that were 18 days of age received an aversive footshock in a novel context. Rats displayed conditioned fear when tested 1 min after training but not 24 hr after training. Systemic injection of the opioid receptor antagonist naloxone prior to test, but not immediately after training, alleviated infantile amnesia. Naloxone also alleviated infantile amnesia when injected prior to test 7 days after training. These effects of naloxone were due to actions on central rather than peripheral opioid receptors and were not due to any tendency of the drug to produce fear or freezing. These results show that central opioid receptors regulate retrieval of fear memories in infant rats.
authors.affiliation: School of Psychology, University of New South Wales, Sydney, Australia.
authors.forename: Marianne
authors.initials: M
authors.lastname: Weber
authors.forename: Gavan P
authors.initials: GP
authors.lastname: McNally
authors.forename: Rick
authors.initials: R
authors.lastname: Richardson
mesh_terms: D000647:Amnesia / Q000188:drug therapy* / Q000503:physiopathology; D000818:Animals; D000831:Animals, Newborn; D003213:Conditioning, Psychological / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005239:Fear / Q000187:drug effects*; D005260:Female; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects; D008297:Male; D008568:Memory / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology / Q000627:therapeutic use; D009292:Narcotic Antagonists / Q000494:pharmacology / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000502:physiology*; D012153:Retention, Psychology / Q000187:drug effects; D013997:Time Factors
chemical_list: D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D009270:Naloxone