Morphine self-administration in μ-opioid receptor-deficient mice

Axel Becker, Gisela Grecksch, Rudolf Brödemann, Jürgen Kraus, Brigitte Peters, Helmut Schroeder, Werner Thiemann, Horace H. Loh, Volker Höllt

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68 Scopus citations


Morphine-induced place preference was demonstrated recently in wild-type mice, whereas this conditioned behaviour was not observed in μ-opioid receptor-deficient mice. In the present study, we investigated locomotor effects of subcutaneously (s.c.) injected morphine as well as intracerebroventricular (i.c.v.) morphine self-administration in μ-opioid receptor-knockout mice. After s.c. morphine injection, locomotor activity significantly increased in wild-type animals. As expected, in the self- administration test the rate of self-administration constantly increased in wild-type mice reflecting reward effects of morphine. This increase was independent of locomotor/motor activity. In contrast, self-administration rates and locomotor/motor activity significantly decreased in the receptor- deficient animals. It was shown that this aversive effect might partly be due to κ-opioid receptor interaction.

Original languageEnglish (US)
Pages (from-to)584-589
Number of pages6
JournalNaunyn-Schmiedeberg's Archives of Pharmacology
Issue number6
StatePublished - Jun 24 2000


  • Locomotor activity
  • Morphine
  • Nor-Binaltorphimine
  • Nose-poke response
  • Self- administration
  • Transgenic mice
  • μ-Opioid receptor

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