The purpose of this project is to determine which second messenger pathways are involved in receptor regulation of rat enkephalin (ENK) levels. The ENK promoter contains two major potential transcription factor sites, the ENKCRE-2 site, which functions as a cAMP (and Ca2+) responsive element (CRE) as well as an AP-1 (Fos/Jun) binding site, and the B-2 (NFKB) site. Glial (and possibly neuronal) ENK levels are known to be increased by elevating cAMP, and we have demonstrated a glucocorticoid potentiation of this stimulation; we are presently trying to better characterize transcription factors involved. We have done much descriptive work in vivo; here however it is difficult to establish the mechanisms involved in ENK regulation. Most of our recent efforts have focused on primary mixed brain cell cultures, a superior system in that all potentially important cells are present, and have found that ENK greatly increases in glia when neurons are removed or killed. This is essentially brain injury in vitro, and we have also found that ENK increases together with other glial markers in some brain areas after kainate-induced injuries. Developmental changes and roles of ENK may also be recapitulated in culture. We hope to determine the pathways (second and third messengers) involved in glial ENK induction after injury.
