Investigative ophthalmology & visual science
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Invest. Ophthalmol. Vis. Sci. · Mar 2006
Randomized Controlled TrialIntravenous administration of diphenhydramine reduces histamine-induced vasodilator effects in the retina and choroid.
Intravenous administration of histamine causes an increase in choroidal blood flow (ChBF) and retinal vessel diameters in healthy subjects. The receptor mediating this response has not yet been identified. The present study was undertaken to clarify whether H1 receptor blockade with diphenhydramine affects the hemodynamic response of histamine in the choroid and the retina. ⋯ The present data confirm that histamine increases ChBF and retinal vessel diameters in healthy subjects. Administration of the H1 receptor blocker diphenhydramine significantly reduced histamine-induced changes in ocular perfusion parameters. These results strongly indicate that in the retina and choroid, H1 receptors are involved in the histamine-mediated hemodynamic effects in vivo.