Estrogen-induced alterations of spinal cord enkephalin gene expression.
Enkephalin-synthesizing neurons in the superficial laminae of the spinal and trigeminal dorsal horn are critical components of the endogenous pain-modulatory system. We have previously demonstrated that these neurons display intracellular estrogen receptors, suggesting that estrogen can potentially influence their enkephalin expression. By using Northern blot, we now show that a bolus injection of estrogen results in a rapid increase in spinal cord enkephalin mRNA levels in ovariectomized female rats. Thus, 4 h after estrogen administration the enkephalin mRNA-expression in the lumbar spinal cord was on average 68% higher (P<0.05) than in control animals injected with vehicle only. A small increase in the amount of enkephalin mRNA was also seen after 8 h (P<0.05), whereas no difference between estrogen-injected and control animals was found after 24 h or at time periods shorter than 4 h. Taken together with the previous anatomical data, the present findings imply that estrogen has an acute effect on spinal opioid levels in areas involved in the transmission of nociceptive information.
Amandusson
A
A
Division of Cell Biology, Department of Biomedicine and Surgery, Faculty of Health Sciences, University of Linköping, S-581 85, Linköping, Sweden.
Hallbeck
M
M
Hallbeck
A L
AL
Hermanson
O
O
Blomqvist
A
A
D000818:Animals; D004745:Enkephalins / Q000235:genetics*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D009474:Neurons / Q000378:metabolism*; D010052:Ovariectomy; D011498:Protein Precursors / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects
D004745:Enkephalins; D011498:Protein Precursors; D012333:RNA, Messenger; D004958:Estradiol; C033660:preproenkephalin