Reduced nNOS expression induced by repeated nicotine treatment in μ-opioid receptor knockout mice

Ji Hoon Yoo, Jae Han Cho, Seok Yong Lee, Horace H. Loh, Ing K. Ho, Choon Gon Jang

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13 Scopus citations


To determine whether neuronal nitric oxide synthase (nNOS) is involved in nicotine-induced behavioral sensitization in μ-opioid receptor knockout mice we adopted an immunohistochemical approach. Our results confirm that repeated nicotine administration increased locomotor activity in wild-type mice, but failed to increase locomotor activity in μ-opioid receptor knockout mice, thus suggesting that the μ-opioid receptor is involved in behavioral sensitization. Higher numbers of nNOS-positive cells were observed in the striatum of wild-type mice repeatedly treated with nicotine than in saline-treated wild-type mice. However, μ-opioid receptor knockout mice showed significantly lower nicotine-induced nNOS expression in the striatum versus wild-type mice. No differences were found in the hilus of the dentate gyrus between wild-type and μ-opioid receptor knockout mice. These findings demonstrate that the absence of μ-opioid receptors can cause a significant reduction in the expression of nNOS in the striatum, as induced by repeated nicotine treatment.

Original languageEnglish (US)
Pages (from-to)70-74
Number of pages5
JournalNeuroscience Letters
Issue number1-2
StatePublished - May 20 2005

Bibliographical note

Funding Information:
This research was supported by a grant (M103KV01000804K220100830) from the Brain Research Center of the 21st Century Frontier Research Program funded by the Ministry of Science and Technology, Republic of Korea.


  • Immunohistochemistry
  • Knockout mice
  • Nicotine
  • Nnos
  • Sensitization
  • μ-Opioid receptors


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