CHROMOGRANIN-A INHIBITS RETINAL DOPAMINE RELEASE

Chromogranin A (CGA), a peripherally active prohormone, is a soluble c omponent in the secretory granules of many endocrine tissues and is co secreted with their peptide or amine hormones. Using an antibody prepa red against purified rat adrenal CGA, immunostaining was localized to the inner and outer plexiform layers of the rat retina and to selected ganglion cells. Exogenous CGA (purified from human adrenals) when app lied to perfused rat retina potently inhibited the potassium-induced r elease of endogenous dopamine (DA). This action was dose-dependent, wi th an IC50 of 3 nM; at 100 nM CGA retinal DA release was completely ab olished.