PACAP IS A POTENT AND HIGHLY EFFECTIVE STIMULATOR OF ADENYLYL-CYCLASEACTIVITY IN THE RETINAS OF DIFFERENT MAMMALIAN-SPECIES

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