Postnatal development of dopamine D-1 receptor immunoreactivity in the ratretina

Dopamine, an important neuromodulator in the retina, controls the balance o f rod cone photoreceptor activity and influences the activity of several in terneurons, The postnatal development of dopaminergic neurons, visualized i mmunocytochemically, was compared to the development of dopamine D-1 recept or immunoreactivity. Expression of D-1 receptors was monitored throughout t he postnatal development of the rat retina using a subtype-specific monoclo nal antibody, D-1 receptors are expressed in the inner plexiform layer begi nning at birth. Labeling of the inner plexiform layer changed from a diffus e pattern, staining the entire layer, to the typical adult punctate stainin g, that was organized in layered bands and occurred in the second postnatal week. The staining did not co-localize with dopaminergic cells; instead, i t colocalized with cells in the inner nuclear layer or the ganglion cell la yer. Within these cells, D-1 receptors were most heavily expressed in proce sses stratifying in the inner plexiform layer. Staining in the outer plexif orm layer and in horizontal cells was found beginning in the second postnat al week. Clustering of the D-1 receptor within plexiform layers, a process typical for the well-described function of dopamine modulation in the adult , occurred late in postnatal development. A possible function of D-1 recept ors in neuronal development is discussed. J, Neurosci, Res. 56:397-404, 199 9, (C) 1999 Wiley-Liss, Inc.