Acute intermittent morphine increases preprodynorphin and kappa opioid receptor mRNA levels in the rat brain.
We determined the effects of morphine on mRNA levels for the opioid ligands preprodynorphin (PPD) and preproenkephalin (PPE) and the kappa opioid receptor (KOR). Rats received six injections of morphine (6.25 mg/kg/injection) every 2 h, and were sacrificed 30 min later. mRNA levels were measured in brain tissue after removal of the cortex, cerebellum and brainstem. There were increases in PPD and KOR mRNA levels (P<0.05 and P<0.005, respectively), with no alteration of PPE. These alterations in the kappa/dynorphin system may counter morphine-induced effects on the brain.
Wang
X M
XM
Laboratory of the Biology of Addictive Diseases, The Rockefeller University, Box 171, 1230 York Avenue, New York, NY 10021, USA.
Zhou
Y
Y
Spangler
R
R
Ho
A
A
Han
J S
JS
Kreek
M J
MJ
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects* / Q000235:genetics; D004399:Dynorphins / Q000235:genetics*; D004745:Enkephalins / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D011498:Protein Precursors / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D017473:Receptors, Opioid, kappa / Q000235:genetics*
D004745:Enkephalins; D009294:Narcotics; D011498:Protein Precursors; D012333:RNA, Messenger; D017473:Receptors, Opioid, kappa; C036448:pre-prodynorphin; D004399:Dynorphins; D009020:Morphine; C033660:preproenkephalin