The retina is a highly complex nervous tissue that converts light into
patterns of electrical action potentials in order to process visual i
nformation. To carry out its function as a transducer and processor of
visual information, the retina must be structurally and biochemically
organized to send a coherent signal to the visual areas of the brain.
In recent years, a number of biologically active substances have been
demonstrated to be located within neurons in the retina. Most of them
are thought to be involved in the modulation of the signal and its tr
ansmission to the brain through the optic nerve. The present paper att
empts to summarize the immunocytochemical distribution and physiology
of some neuronally localized substances in the mammalian retina, namel
y dopamine and neuropeptides.