Natriuretic peptides are localized to rat retinal amacrine cells

Natriuretic peptides (NPs) may act as neuromodulators through activation of three specific receptor subtypes (NPRs). In the present study we examined the expression of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) on different subtypes of retinal amacrine cells (ACs) in rat by immunofluoresecence double labeling. All three NPs were moderately expressed in dopaminergic and cholinergic ACs, stained by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT), respectively. The immunostaining appeared on the membrane, cytoplasm and somatodendritic compartments of these ACs. In AII glycinergic ACs, labeled by parvalbumin (PV), however, only faint punctate staining, if any, was seen. These results suggest that NPs could be produced in ACs and play a neuromodulatory role in the inner retina. Together with a previous immunocytochemical study, showing that NPR-B is present in cultured rat GABAergic ACs, our results further suggest that NPs produced in ACs may also modulate their own activity.