Reduced nNOS expression induced by repeated nicotine treatment in mu-opioid receptor knockout mice.
To determine whether neuronal nitric oxide synthase (nNOS) is involved in nicotine-induced behavioral sensitization in mu-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 mu-opioid receptor knockout mice, thus suggesting that the mu-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, mu-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 mu-opioid receptor knockout mice. These findings demonstrate that the absence of mu-opioid receptors can cause a significant reduction in the expression of nNOS in the striatum, as induced by repeated nicotine treatment.
Yoo
Ji-Hoon
JH
Department of Pharmacology, College of Pharmacy, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon 440-746, Republic of Korea.
Cho
Jae-Han
JH
Lee
Seok-Yong
SY
Loh
Horace H
HH
Ho
Ing K
IK
Jang
Choon-Gon
CG
D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D018929:Cell Culture Techniques / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects*; D007150:Immunohistochemistry / Q000379:methods; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009538:Nicotine / Q000008:administration & dosage*; D018722:Nicotinic Agonists / Q000008:administration & dosage*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D017450:Receptors, Opioid, mu / Q000172:deficiency*; D013997:Time Factors
D009419:Nerve Tissue Proteins; D018722:Nicotinic Agonists; D017450:Receptors, Opioid, mu; D009538:Nicotine; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse