Chronic morphine increases biosynthesis of nitric oxide synthase in the rat spinal cord.
The present study was undertaken to determine the influence of chronic morphine treatment on the biosynthesis of nitric oxide synthase (NOS) in the rat spinal cord using in situ hybridization and immunohistochemical methods. Repeated administration of morphine (20-100 mg/kg/day; 10 days) increased the NOS mRNA level in laminae I-IV and X 3 h after the last injection. That effect was accompanied by an increase in both the number of NOS-positive cells (24 h) and the optical density of NOS-immunoreactivity (3 and 24 h). The results indicate that repeated morphine administration increases NOS biosynthesis in the rat spinal cord, which may reflect adaptive changes accounting for development of opiate tolerance and dependence.
Machelska
H
H
Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow.
Ziólkowska
B
B
Mika
J
J
Przewlocka
B
B
Przewlocki
R
R
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D013997:Time Factors
D000701:Analgesics, Opioid; D009020:Morphine; D019001:Nitric Oxide Synthase