PACAP is a potent and highly effective stimulator of adenylyl cyclase activity in the retinas of different mammalian species.

In rat, calf, pig and rabbit retinas the two forms of pituitary adenylate cyclase activating polypeptide with 38- and 27-amino acids (PACAP-38 and PACAP-27) produce a robust stimulation of adenylyl cyclase activity. PACAP-38 acts at picomolar concentrations and is generally more potent than PACAP-27. Both PACAPs are systematically more effective than the structurally homologous vasoactive intestinal peptide. Moreover, rat, calf and pig retinas contain significant amounts of PACAP-38 immunoreactivity. This study provides the first evidence for the action and occurrence of PACAP in mammalian retinas.