Sustained increases in activating transcription factor-2 and activator protein-2 in the rat supraoptic nucleus during...

During increases in plasma osmolality, extrinsic and intrinsic stimuli converge on the neuroendocrine cells within the supraoptic nucleus (SON) and paraventricular nucleus and evoke the release of vasopressin (VP). This release is accompanied by an increase in VP synthesis, but the signal transduction pathways that coordinate these two processes are still poorly understood. Several transcription factors have been suggested to be intermediates in this process, but their expression is often transient in spite of continued VP synthesis. Transcription factor expression during chronic neuroendocrine cell stimulation has rarely been examined. In an effort to identify sustained increases, we examined the expression of several transcription factors in the SON of normal rats and rats deprived of water for 44 h. Alpha and beta isoforms of activator protein-2 (AP-2 alpha; AP-beta), activating transcription factor-2 (ATF-2), the phosphorylated form of cyclic AMP response element binding protein and phospho-cJun were all expressed in the rat SON under basal conditions. Increases in AP-2 alpha and ATF-2 were sustained throughout the SON during water deprivation, suggesting that these transcription factors could play a role in the maintenance of VP and oxytocin gene transcription in response to dehydration.