Chronic morphine increases mu-opiate receptor binding in rat brain: a quantitative autoradiographic study.
Quantitative autoradiography was used to show the locations of mu-opiate receptor binding sites which are upregulated following chronic morphine treatment in rats. A saturating concentration of the mu-specific ligand [3H]D-ala2-N-methyl-Phe4,Gly-ol5-enkephalin was used to label sites in slide-mounted sections through one level of the thalamus in rats implanted subcutaneously with morphine pellets for 5 days. In vitro binding and autoradiography showed the largest increase in binding in the hypothalamus, especially the ventromedial nucleus (155%), with smaller increases in the basolateral and medial amygdaloid nuclei and the striatum. The set of structures showing the upregulation appears to be a subset of those upregulated by opiate antagonists, but there appears to be no correlation of the mu-sites showing upregulation with other anatomical features of the brain opiate system. The physiological significance of the upregulation is not known at present.
Brady
L S
LS
Unit on Functional Neuroanatomy, NIMH, Bethesda, MD 20892.
Herkenham
M
M
Long
J B
JB
Rothman
R B
RB
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004343:Drug Implants; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009021:Morphine Dependence / Q000378:metabolism; D009928:Organ Specificity; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D017450:Receptors, Opioid, mu; D012016:Reference Values; D014316:Tritium
D004343:Drug Implants; D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D014316:Tritium; D009020:Morphine