The Role And Mechanism Of AQP4in Retinal Electrophysiology And In Laser-induced Ocular Hypertension

Objective. To investigate the retinal ganglion cell (RGC) dysfunction triggeredby knock out (KO) of aquaporin4(AQP4) with pattern electroretinogram (PERG),and to establish a laser-induced model of ocular hypertension in AQP4knockout mice(CD1background). Then explain the role and mechanism of AQP4in retinalelectrophysiology and in laser-induced model of ocular hypertension.Methods.1. The animals were anesthetized with intraperitoneal injections of2%chloral hydrate (0.2ml/10g). A simultaneous recording of PERG were performed byhomemade electrodes in both AQP4KO mice (n=18) and WT mice (n=18).2.Unilateral ocular hypertension was induced in KO (n=18) and WT (n=18) mice bylaser photocoagulation of limbal and episcleral veins. IOP was measured with theIcareLAB rebound tonometer (RBT) before and after surgery. Observe the alternationof the IOP levels.Results.1. In AQP4KO mice, the mean P50amplitudes was (5.53±1.31) uV, themean N95amplitudes was (7.71±1.89) uV. In WT mice, the mean P50amplitudeswas (8.14±1.24) uV, the mean N95amplitudes was (11.30±2.61) uV. The amplitudesof AQP4KO mice had a markedly reduction in both P50and N95when comparedwith WT mice (P＜0.01), and the latencies of AQP4KO mice in both P50and N95were shorter than that of WT.2. The mean IOP in animals under general anesthesiaand before photocoagulation was (6.61±0.90) mmHg in KO mice (n=18×2) and (7.31±0.98) mmHg in WT mice (n=18×2). IOP in KO mice mildly but significantlylower when compare with IOP in WT mice (P＜0.05). One day after surgery, themean IOP was (14.78±1.80) mmHg (operated, n=18) in KO mice;(16.44±1.46)mmHg (operated, n=18) in WT mice. There was a markedly increase of the IOP by1day after operation, to twice its baseline value that remained elevated for thefollowing seven days and decreased gradually to baseline values at about day eight.The degree of IOP change almost the same between KO and WT mice, but the mildlydifference presence all the time (P <0.05).Conclusions.1. PERG does a good response to the function of RGCs. AQP4nullmaybe have do something harm to the RGC, retinal function could have beenimpaired in AQP4KO mice.2. Transient elevation of IOP was induced by laserphotocoagulation of limbal and episcleral veins. The ocular hypertension model ofAQP4KO mice could provide some useful evidence for finding a novel approach forthe treatment of elevated IOP by inhibiting the expression of AQP4.