Abstract
The retina is a light-sensitive tissue of the central nervous system that is vulnerable to ischemia. The pathological mechanism underlying retinal ischemic injury is not fully understood. The purpose of this study was to investigate structural and functional changes of different types of rat retinal neurons and visual behavior following transient global ischemia. Retinal ischemia was induced using a 4-vessel occlusion model. Compared with the normal group, the number of βIII-tubulin positive retinal ganglion cells and calretinin positive amacrine cells were reduced from 6 h to 48 h following ischemia. The number of recoverin positive cone bipolar cells transiently decreased at 6 h and 12 h after ischemia. However, the fluorescence intensity of rhodopsin positive rod cells and fluorescent peanut agglutinin positive cone cells did not change after reperfusion. An electroretinogram recording showed that the a-wave, b-wave, oscillatory potentials and the photopic negative response were completely lost during ischemia. The amplitudes of the a- and b-waves were partially recovered at 1 h after ischemia, and returned to the control level at 48 h after reperfusion. However, the amplitudes of oscillatory potentials and the photopic negative response were still reduced at 48 h following reperfusion. Visual behavior detection showed there was no significant change in the time spent in the dark chamber between the control and 48 h group, but the distance moved, mean velocity in the black and white chambers and intercompartmental crosses were reduced at 48 h after ischemia. These results indicate that transient global ischemia induces dysfunction of retinal ganglion cells and amacrine cells at molecular and ERG levels. However, transient global ischemia in a 17 minute duration does not appear to affect photoreceptors.
Highlights
The retina is a light-sensitive tissue of the central nervous system
We found that transient global ischemia, the 4-vessel occlusion (4-VO) model, induced selective neuronal death and changes in dendritic and synaptic plasticity in the hippocampus [17,18,19,20]
No obvious changes in the morphology of cells in the ganglion cell layer (GCL), inner nuclear layer (INL) and outer nuclear layer (ONL) of the retina were observed after ischemia
Summary
The retina is a light-sensitive tissue of the central nervous system. There are several types of cells in the retina; photoreceptors (rods and cones), located close to the outer surface of the retina, receive light stimulation and convert light into electrical signals; retinal ganglion cells (RGCs), near the inner retinal surface, transmit visual signals to the visual cortex and other higher visual centers; interneurons (bipolar cells and amacrine cells), located between the photoreceptors and ganglion cells, transmit signals from the photoreceptors to the RGCs [1].Functional signals and activities of each cell type can be recorded by the electroretinogram (ERG). The visual function of the retina can be evaluated by different behavioral methods, such as startle reflex tests [8], orientation test [9], Y-maze for visual testing [10], and the optokinetic reflex [11]. These techniques have been used to detect either eye movement or navigation ability, which is affected by vision. One apparatus consisted of several compartments including a curved tube, one introduction chamber, two escape alleys, three swing doors and one home cage This apparatus was designed to train rats to distinguish two different visual stimuli [12]. Because the structure of this apparatus was adequate and simpler than the other apparatus mentioned above, it was employed in the present study to detect whether transient global ischemia affects light reception
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