Effects of post-trial administration of naloxone and β-endorphin on shock-induced fighting in rats

A. Tazi, R. Dantzer, P. Mormède, M. Le Moal

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

To study the involvement of endogenous opioid peptides in the development of shock-induced fighting, naloxone (2 mg/kg) or β-endorphin (10 μg/kg) was administered subcutaneously immediately after the session and during nine consecutive daily sessions to rats repeatedly exposed to electric shocks. β-Endorphin blocked the development of shock-induced fighting while naloxone facilitated it but only when shock-induced fighting occurred at a low rate. The effects of β-endorphin were time dependent since when β-endorphin was injected 90 min after the shock session instead of immediately after, its impairing effect disappeared. In addition, naloxone blocked the impairment produced by β-endorphin. Differential postsession treatment of each member of pairs of rats with naloxone and β-endorphin resulted in a higher probability of rats treated with naloxone to be dominant over rats treated with β-endorphin in the test situation. These results are discussed in relation with the possible involvement of endogenous opioids in the modulation of the physiological consequences of defensive behavioral response to shock.

Original languageEnglish (US)
Pages (from-to)192-202
Number of pages11
JournalBehavioral and Neural Biology
Volume39
Issue number2
DOIs
StatePublished - Nov 1983
Externally publishedYes

ASJC Scopus subject areas

  • Physiology

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