Estrogen-induced alterations of spinal cord enkephalin gene expression

Abstract
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 (PP