Intraocular pressure (IOP) has a tendency to fluctuate throughout the day, reaching its peak\nin the early morning in healthy subjects or glaucoma patients. Likewise, histamine tone also fluctuates\nover time, being lower at nighttime. Numerous studies have demonstrated a correlation between\nshort-term IOP fluctuation and glaucoma progression; however, it has not yet been determined\nwhether histamine plays a role in IOP fluctuations. The aim of this research was to establish the\ndistribution of the histamine receptor proteins and respective mRNAs in the eye by western blot,\nimmunohistochemistry and RT-PCR in New Zealand rabbits. Furthermore, we used a transient ocular\nhypertension (OHT) model induced by injection of 50 microL of 5% hypertonic saline into the vitreous\nand a stable OHT model (100 microL 0.1% carbomer in the anterior chamber) to address the potential\nIOP-lowering ability of H3 receptor (H3R) antagonists (ciproxifan, DL76 and GSK189254). IOPs were\nperformed with a Tono-Pen at baseline and 60, 120 and 240 min post treatment after transient OHT\ninduction and, every day for 12 days in the stable OHT model. All histamine receptor subtypes were\nlocalized in the rabbit retina and ciliary body/trabecular meshwork. All the treatments lowered IOP\nin a dose-dependent fashion between 0.3% and 1%. More specifically, the effects were maximal with\nciproxifan at 60 min post-dose.....................
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