Abstract
Purpose::
Memantine, a use-dependent NMDA channel blocker, is currently being evaluated in patients with chronic open angle glaucoma. Patients with an acute glaucoma attack often experience a decrease in visual acuity. The purpose of this study was to determine the effect of a single oral dose of memantine on reduced sweep visual evoked potential (VEP) thresholds produced by an acute elevation of IOP in pigmented rabbits.
Methods::
Eleven Dutch-belted rabbits weighing 2.5 - 3kg each were divided into 2 groups. One group (n=5) received memantine (50mg) and the other group (n=6) received sugar (50mg) 2 hours prior to raising the IOP in the OD to 120 mmHg for 45 minutes; OS were untreated. Four months after the insult, the sweep VEP technique, adapted for conscious animals, was used to determine OD and OS thresholds in each animal. Stimuli were vertical gratings, 7.5Hz temporal frequency, 80% contrast and peak luminance of 600cd/m2. VEPs were obtained from 4 permanent stainless steel electrodes implanted over the occipital cortex. In each 10-second trial, spatial frequency of the grating changed linearly every second from 0.1 to 5 cycles per degree (cpd).
Results::
Sweep VEP thresholds in OD and OS of placebo-treated animals were 1.78 ± 0.18 cpd and 2.32 ± 0.08 cpd, respectively, for a difference of -24 ± 6%. The corresponding values for the memantine-treated group were 2.24 ± 0.18 cpd and 2.23 ± 0.23 cpd, for a difference of 3 ± 10%; p = 0.04 vs placebo.
Conclusions::
Oral memantine normalized the sweep VEP deficit following an acute elevation of IOP.
Keywords: neuroprotection • electrophysiology: non-clinical • photoreceptors: visual performance