Estradiol increases glucocorticoid binding and glucocorticoid induction of ornithine decarboxylase in the rat spinal cord.

Previous results demonstrated that estradiol (E2) treatment of ovariectomized-adrenalectomized (OVX-ADX) rats increased glucocorticoid (GC) binding in brain regions. The experimental protocol was extended to the spinal cord, a GC target tissue in which ornithine decarboxylase (ODC) is markedly induced by GC treatment. First, we measured GC binding to type I and type II receptors in ventral horn, dorsal horn and lateral funiculus of OVX-ADX rats treated during 4 days with E2 or vehicle. In E2-treated rats, type II receptors increased solely in dorsal horn, whereas type I sites remained unchanged. Second, in a group of OVX-ADX rats receiving dexamethasone (DEX), pretreatment with E2 superinduced ODC in ventral horn and lateral funiculus, but not in dorsal horn. Third, we found that the dorsal horn was relatively enriched in E2 receptors compared to other areas. Therefore, E2 stimulation of GC binding to type II sites may be mediated through E2 receptors localized in the dorsal horn. We suggest that combined treatment with E2 and DEX employs a transsynaptic mechanism for ODC induction at the ventral horn and lateral funiculus, with hormonal interaction taking place at the dorsal horn level.