Immunohistochemical localization of cyclic AMP-responsive element binding protein (CREB)-binding protein in the pig retina during postnatal development

This study evaluated the cellular localization of cyclic AMP-responsive element binding protein-binding protein (CBP) expression in pig retinas during postnatal development. Immunohistochemistry and Western blot analysis were performed on retinal tissue from 2-day-old, 5-week-old, and 6-month-old pigs. Western blot analysis detected the expression of CBP in the retinas of 2-day-old piglets and showed that it was significantly decreased in the retinas of 5-week-old and 6-month-old pigs. Immunohistochemically, CBP was intensely immunostained in protein kinase C alpha (PKC${\alpha}$)-positive-bipolar cells, glutamine synthetase-positive M$\ddot{u}$ller cells, and in ganglion cells in 2-day-old piglets. CBP was detected weakly in the inner plexiform, outer nuclear, and rod and cone layers. CBP immunoreactivity in the ganglion cell layer was decreased in the retinas of 5-week-old and 6-month-old pigs, while clear CBP expression detected in the neurite of PKC${\alpha}$-positive bipolar cells in the inner nuclear layer. In addition, CBP immunoreactivity in M$\ddot{u}$ller cells and glial fibrillary acidic protein-positive glial processes was particularly noteworthy in pig retinas, but not in rat retinas. Th e results indicate that CBP is expressed differentially in the retinal neurons and glial cells according to growth and animal species, and may play an important role in homeostasis in M$\ddot{u}$ller cells, neurite extention in bipolar cells, and signal transduction in photoreceptor cells in the porcine retina.