Morphine activation of c-fos expression in rat brain.
The post-receptor mechanism of opiate action has been studied by examining the activation by morphine of the proto-oncogene c-fos and its encoded nucleoprotein pp55c-fos (FOS) in rat caudate-putamen, which is rich in the mu-type opiate receptor. Following an acute morphine treatment, c-fos mRNA levels in rat caudate-putamen were increased to maximum (420% of control level) at 45 minutes and returned to control levels at 90 minutes. This induction was completely abolished by naloxone, a morphine antagonist. Fos protein, detected by immunocytochemistry, was also increased 3 hours after morphine injection, in the caudate-putamen, but not in the olfactory tubercle, which does not have the mu-type opiate receptor. Upon activation of opiate receptors by morphine, the c-fos gene is activated and Fos protein may act as a signal transducer uniquely involved in the mechanism of opiate addiction at the level of gene regulation.
Chang
S L
SL
Department of Anatomy, Tulane University Medical Center, New Orleans, LA 70112.
Squinto
S P
SP
Harlan
R E
RE
D000818:Animals; D015152:Blotting, Northern; D001921:Brain / Q000502:physiology*; D002421:Caudate Nucleus / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D007124:Immunoenzyme Techniques; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016760:Proto-Oncogene Proteins c-fos; D011699:Putamen / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats
D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D009270:Naloxone; D009020:Morphine