Effect of melatonin on vascular responses of porcine ciliary arteries

Purpose. To investigate the effect of melatonin on isolated porcine ciliary arteries. Methods. Isolated porcine ciliary arteries were suspended in myograph chambers filled with modified Krebs-Ringer solution (37°C; 95% O 2 /5% CO 2) for isometric tension recording. Results. In quiescent porcine ciliary arteries with endothelium, melatonin (10 -11 –10 -5 M) evoked no change in vascular tone. The highest concentration of melatonin (10 -4 M) evoked a small but significant contraction. In vessels pre-contracted with U-46619 (10 -7 M), increasing concentrations of melatonin (10 -11 –10 -5 M) did not evoke a response. In pre-contracted arteries with endothelium, contractile response of vascular smooth muscle to increasing concentrations of serotonin (10 -10 –10 -5 M) and noradrenaline (10 -10 –10 -5 M) was reduced after preincubation with melatonin (10 -4 M). Melatonin (10 -4 M) did not alter the response to endothelin-1 (10 -10 –10 -7 M) and U-46619 (10 -10 –10 -6 M) in precontracted arteries with endothelium....