Acute "binge" cocaine increases mu-opioid receptor mRNA levels in areas of the rat mesolimbic mesocortical dopamine system.
Autoradiography studies demonstrated that chronic "binge" cocaine administration increased mu-opioid receptor density in dopaminergically innervated rat brain regions, including the cingulate cortex, the nucleus accumbens, and the basolateral amygdala. The present study investigated the effects of a single day of binge-pattern cocaine administration (3 x 15 mg/kg, intraperitoneally [i.p.] at hourly intervals) on mu-opioid receptor mRNA levels in selected brain regions. Rats were sacrificed 30 min after the third injection and mRNA levels were measured by a quantitative solution hybridization RNase protection assay. Acute binge cocaine administration significantly increased mu-opioid receptor mRNA levels in the frontal cortex, nucleus accumbens, and amygdala, but not in the caudate-putamen, thalamus, hippocampus, and hypothalamus. As has been suggested for other G-protein coupled receptors, the rapid increase of MOR mRNA reported in this study might represent an adaptive response to compensate for a decrease in number of receptors following cocaine-induced opioid peptide release.
Yuferov
V
V
Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY 10021, USA. yuferov@rockvax.rockefeller.edu
Zhou
Y
Y
Spangler
R
R
Maggos
C E
CE
Ho
A
A
Kreek
M J
MJ
D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism*; D003042:Cocaine / Q000008:administration & dosage* / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008032:Limbic System / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D017450:Receptors, Opioid, mu / Q000235:genetics*; D013997:Time Factors; D014018:Tissue Distribution / Q000502:physiology
D012333:RNA, Messenger; D017450:Receptors, Opioid, mu; D003042:Cocaine; D004298:Dopamine