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Abstract: Background: Both in vivo and in vitro studies suggest that excess stimulation of non-NMDA receptors can result in massive neuronal death in the retina. In particular, murine amacrine neurons have been known to show marked susceptibility to the toxic effects of kainate. Purpose: This study was designed to examine and characterize the role of N-methyl-d-aspartate (NMDA) receptor vs non-NMDA receptor in glutamate-induced neurotoxicity in the retina.  Methods: Primary cultures obtained from fetal rat retina (gestation day 16–19) were used for the experiment. The neurotoxicity was assessed quantitatively using the trypan blue exclusion method. Electrophysiological studies using patch-clamp techniques were performed to record whole-cell currents evoked by these excitatory amino acids.  Results: Removal of extracellular Ca2+ from the medium or application of MK-801 reduced the extent of cell death induced by the brief exposure to glutamate, NMDA, and kainate. By contrast, cell death induced by a 60-min exposure to kainate was not affected by MK-801. The electrophysiological study demonstrated that MK-801 abolished the whole-cell currents evoked by NMDA but had no effect on those induced by kainate or AMPA. Conclusion: These findings demonstrate that brief exposure to kainate induces cell death by way of activating NMDA receptors in cultured fetal retinal neurons and that NMDA receptors are the predominant route of fetal retinal neurotoxicity induced by brief glutamate exposure.

Abstract: Background: The purpose of this study is to report a case of superior oblique paresis and contralateral relative afferent pupillary defect (RAPD) with normal vision in a patient with brainstem astrocytoma. Methods: We correlated the pa-tient’s clinical findings with anatomical substrates on magnetic resonance imaging (MRI) findings. Results: The patient had right-sided superior oblique paresis. There was a left-sided RAPD, although visual acuities and visual fields were normal in both eyes. T1-weighted, gadolinium-enhanced MRI demonstrated a hyperintense area in the right dorsal midbrain. Conclusion: It is suggested that the lesion damaged both the pretectal afferent pupillary pathway and fascicles of the trochlear nerve, causing a unique combination of neuro-ophthalmologic findings.