Ngfi-a immunoreactivity in the primate retina: implications for genetic regulation of plasticity

In rodents, enriched environments drive the expression of the immediate early gene NGFI-A, a regulator of the plasticity marker Synapsin I. Both proteins have been implicated as mediators of plasticity in the rat mammalian retina. In the present work immunocytochemistry directed against these proteins was used to explore their basal activity in the retina of a more visual species, the New World monkey Cebus apella. In contrast to rat, monkey retina displayed high basal expression of both NGFI-A and Synapsin I. The greatest number of NGFI-A -expressing cells was observed within the inner nuclear layer, although NGFI-A positive nuclei were also found in the ganglion cell layer. High levels of Synapsin I were found in the inner plexiform layer and outer plexiform layer. Our findings are consistent with the postulate that the retinas of highly visual animals may experience ongoing reorganization as part of normal visual processing, and that NGFI-A and Synapsin I may be well positioned to regulate some of these changes.