Distribution of CREB-binding protein immunoreactivity in the adult rat brain

We demonstrate the expression of the co-activator CREB-binding protein (CBP ) in the nuclei of a large number of neurons and glial structures in the ra t brain and spinal cord. Immunoblotting of nuclear extracts revealed a sing le band at 265 kDa, the size of CBP. We found that CBP immunoreactivity was localized to cholecystokinin mRNA-expressing neurons in the hippocampus an d the thalamus, suggesting that CBP may be involved in long-term memory and modulation of cortical activity. However, CBP-labeling was not ubiquitous, and many brain regions, including several mesencephalic and diencephalic n uclei, showed sparse labeling. Further, the number of neurons displaying in tense CBP-labeling varied across animals in some regions, e.g., the hippoca mpus and the amygdala. Since competition for limited amounts of CBP and CBP -related molecules has been shown to be important for the integration of in tracellular signaling pathways with transcriptional regulation, the present results suggest that varying endogenous levels of CBP in post-mitotic neur ons is an important parameter in neuronal transcriptional regulation. (C) 1 999 Elsevier Science B.V. All rights reserved.