Relationship between morphine and etonitazene-induced working memory impairment and analgesia

Daniela Braida, Enzo Gori, Mariaelvina Sala

Research output: Contribution to journalArticlepeer-review


An 8-arm radial maze task was used to assess the possible role of the opiate system in the spatial memory of the rat. Increasing doses of etonitazene (0.005-0.06 mg/kg i.p.) and morphine (2.5-100 mg/kg i.p.) significantly impaired performance in the working memory components of the task. For both drugs this impairment was linearly related to the log of the administered dose, and the log-dose relationships were parallel. The regression lines calculated for each parameter for both drugs were parallel thus allowing us to calculate the potency: etonitazene proved to about 1000 times more potent than morphine in terms of correct arm entries, the number of errors and the total time taken to complete the task. Moreover, the progressive cognitive impairment produced by both opiates was closely related to an increase in analgesic effect. Pretreatment with naloxone (5 mg/kg i.p.) completely antagonised the disruptive effect of the opiates on working memory. The importance of the μ subtype opiate receptor in cognitive processes is discussed.

Original languageEnglish
Pages (from-to)497-504
Number of pages8
JournalEuropean Journal of Pharmacology
Issue number2-3
Publication statusPublished - Dec 27 1994


  • Etonitazene
  • Memory
  • Morphine
  • Naloxone
  • Opioid
  • Radial maze

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Pharmacology


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