Topical Application of Melatonin Analogue Neu-P11 Reduces Intraocular Pressure in Normotensive Rabbit

Purpose: Melatonin is involved in regulation of intraocular pressure (IOP). In this study, we evaluated the effect of melatonin and its agonist, Neu-P11, on IOP in ocular normotensive rabbit eyes. Material and Methods: A multiple-dose (10^-14 mol/L ~ 10^-5 mol/L; 10μl) study was performed in 30 male New Zealand white rabbits. Melatonin or Neu-P11 was applied topically, and IOP was measured for 7 hours and before experiment without any treatment as resting IOP. Results: Resting IOP was 20.65 ± 3.80 mmHg valued at 100%.Topical application of melatonin or Neu-P11 produced dose-dependent reduction in IOP. Moreover, when the dose exceeded 10^-9 mol/L, Neu-P11 treatment group produced more significant decline in IOP compared with melatonin treatment group (P <;0.05). In the next series, we selected the optical dose of melatonin or Neu-P11 at 50 μM (10^-5 mol/L, 10 μL), it was observed that both melatonin and Neu-P11 treatment rapidly reduce IOP at 0.5 hour, and maximally at 1 hour by 34 ±3.83% vs. 42% ±3.88% decrease of the resting IOP, and IOP valued at 13.65 ± 1.28 mmHg and 11.99 ± 1.45 mmHg, respectively (p<;0.05). And IOP reduction lasted 5 h in Neu-P11 group, in comparison with 3 h in melatonin group. Conclusion: Neu-P11 can be considered as a potential hypotensive substance for treatment of ocular hypertension.