EVIDENCE FOR A POSSIBLE SYNERGISM BETWEEN PITUITARY ADENYLATE-CYCLASEACTIVATING POLYPEPTIDE AND CALCITONIN-GENE-RELATED PEPTIDE IN PORCINEOPHTHALMIC ARTERY

The activities of pituitary adenylate cyclase activating polypeptide ( PACAP) and calcitonin gene-related peptide (CGRP) were investigated in isolated segments of porcine ophthalmic artery, In artery segments pr e-contracted by prostaglandin F-2 alpha, PACAP induced a concentration dependent relaxation, but was clearly less potent than CGRP, When 2 x 10(-10) M CGRP (relaxation 4.3 +/- 0.8%, n = 11) and 10(-8) M PACAP ( relaxation 12.4 +/- 3.8%, n = 10) were added together, the subsequent relaxation was substantially increased (33.6 +/- 5.6%, p < 0.0005), In addition, the rate of relaxation was increased, The results indicate that there is synergism between low concentrations of CGRP and PACAP i n isolated porcine ophthalmic artery.