Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/194053
Type: Artigo de periódico
Title: Effects Of Naltrexone And Cross-tolerance To Morphine In A Learned Helplessness Paradigm.
Author: Teixeira, N A
Pereira, D G
Hermini, A H
Abstract: Opiates have been implicated in learned helplessness (LH), a phenomenon known to be related to opiate stress-induced analgesia (SIA). In the present study, we investigated the role of opiates in the induction of LH and SIA under different conditions. Adult female Wistar rats were trained either by receiving 60 inescapable 1-mA footshocks (IS group, N = 114) or by confinement in the shock box (control or NS group, N = 92). The pain threshold of some of the animals was immediately evaluated in a tail-flick test while the rest were used 24 h later in a shuttle box experiment to examine their escape performance. The opiate antagonist naltrexone (0 or 8 mg/kg, ip) and the previous induction of cross-tolerance to morphine by the chronic administration of morphine (0 or 10 mg/kg, sc, for 13 days) were used to identify opiate involvement. Analysis of variance revealed that only animals in the IS group demonstrated antinociception and an escape deficit, both of which were resistant to the procedures applied before the training session. However, the escape deficit could be reversed if the treatments were given before the test session. We conclude that, under our conditions, induction of the LH deficit in escape performance is not opiate-mediated although its expression is opiate-modulated.
Subject: Analgesia
Analgesics, Opioid
Animals
Drug Tolerance
Female
Helplessness, Learned
Morphine
Naltrexone
Narcotic Antagonists
Rats
Rats, Wistar
Rights: aberto
Identifier DOI: 
Address: http://www.ncbi.nlm.nih.gov/pubmed/9292116
Date Issue: 1997
Appears in Collections:Artigos e Materiais de Revistas Científicas - Unicamp

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