[Effects of serotonin on reactivity of ocular vasculature]

Serotonin presents specific receptors of many types and subtypes. The aim of this study was to analyze the differences in reactivity between the vessels (arteries and veins) of the iris and conjunctiva. The vascular diameter was measured using a noninvasive technique after intraocular administration of different doses of serotonin.

The tests were performed on rats, divided in control and study groups. The modifications of studied vessels' diameters before and after topical administration of the solutions were evaluated by measuring these diameters at fixed time intervals of 30 seconds, for 6 minutes. Differentiation between arteries and veins was made using topical administration of felodipine after the testing 6 minutes interval The statistical significance of differences between the values obtained in each interval of 30 seconds and the control values at the initial moment was evaluated using t-test, the "paired" variant.

There were obtained differences in reactivity between iris and conjunctival vessels and between iris arteries and veins for the different concentrations of tested serotonin solutions.

Iris and conjunctival vessels contain serotonin receptors with different types and densities, whose activation produced vasoconstriction in both territories, but with different evolution and intensity. Differences in reactivity were found between iris arteries and veins, probably due to a different density of receptors between those two territories. The different vascular response might be a protective mechanism against dissemination of conjunctival infections.