Localization of neuroactive substances in the vertebrate retina: evidence for lamination in the inner plexiform layer.

The inner plexiform layer (IPL) of the vertebrate retina is a multilaminated region containing bipolar, amacrine, interplexiform and ganglion cell processes. Immunohistochemical methods clearly demonstrate the existence of various neuroactive substances in distinct morphological types of amacrine cells. Sufficient detail in the staining consistently delineates processes containing these neuroactive substances in multiple laminae of the IPL. Thus, the histochemical approach provides a powerful tool for the analysis of the laminar organization of the IPL and can also be used to further clarify the functional role of various transmitter and peptide substances in the retina.