Peptides influence retinal ganglion cells.

Neurotensin, substance P and (D-Ala2, Met5)-enkephalinamide were iontophoresed onto ganglion cells of the amphibian retina. Substance P and neurotensin were found to be excitatory while (D-Ala2, Met5)-enkephalinamide suppressed all types of ganglion cells. These findings are consistent with a functional role for peptides in the vertebrate retina.