The Role of Histamine and Serotonin in the Control of Vascular Motricity of the Anterior Ocular Segment - Review of the Literature from 1997 to 2018

Abstract

Histamine and serotonin, besides known systemic effects, can influence vascular tone at the eye level. The review of the literature from 1997 to 2018 suggests that these ocular effects are very variable -both vasodilation and vasoconstriction. Specifi c agonists or antagonists acting in the histamine and serotonin domains, are probably more useful than endogenous substances as working tools for discovering the functional elements involved in regulating ocular vascular tone. Knowing that intraocular pressure regulation also depends on the vascular tone of the anterior ocular segment, some of the substances under review may be candidates for potential intraocular pressure lowering drugs. RezumatHistamina și serotonina, pe lângă efectele sistemice cunoscute, pot influenţa tonusul vascular de la nivel ocular. Recenzia literaturii de specialitate din perioada 1997-2018 a arătat că aceste efecte oculare sunt foarte variabileatât vasodilataţie, cât și vasoconstricţie. Substanţele care modulează la nivel de receptor aceste efecte (agoniștii și antagoniștii histaminergici și serotoninergici) sunt probabil mai utili decât substanţele endogene ca instrumente de lucru pentru descoperirea elementelor funcţionale implicate în reglarea tonusului vascular ocular. Cunoscând că reglarea presiunii intraoculare depinde și de tonusul vascular al segmentului anterior ocular, unele din substanţele recenzate ar putea prezenta și efecte hipotonizante oculare.

The histaminergic control of the iridal vascular tone in rats and its influencing by topical administration of olopatadine and ranitidine

“…Very few have used ranitidine or other H2 blocker and practically there are no studies about the effect of olopatadine on the iridal vascular tone. Other H1 receptor blocking agents have been used, like diphenhydramine, pyrilamine and promethazine, but the results of these studies have as a disadvantage the lack of selectivity on histamine H1 receptors, whereas olopatadine is a selective H1 receptor antagonist [ 7 , 15 ]. Further studies are needed to elucidate the effects of histaminergic substances on iris vasculature, using combinations of exogenous histamine and histamine receptor blockers.…”