The effect of AQP4 knock out on retinal electrophysiology in laser-induced ocular hypertension mice

Abstract

To investigate the effect of aquaporin 4 (AQP4) knock out (KO) on the dysfunction of retinal ganglion cells (RGC) in laser-induced ocular hypertension (OHT) mice. Experimental study. AQP4 KO mice (n = 18, 36 eyes) and wide type (WT) mice (n = 18, 36 eyes) were used. Unilateral OHT was induced by laser photocoagulation in KO and WT mice after anesthesia. A simultaneous recording of PERG was performed by homemade electrodes. Intraocular pressure (IOP) was measured with an IcareLAB rebound tonometer every day at noon before and after surgery. The data was analysed by ANOVA and t test. In AQP4 KO mice, the mean P50 and P95 amplitudes were significantly (P < 0.01) reduced compared with WT mice [P50: KO: (5.53 ± 1.31) vs WT: (8.14 ± 1.24) µv t = 5.70 and P95: KO: (7.71 ± 1.89) vs WT: (11.30 ± 2.61) µv, t = 3.83, respectively]. The latencies of AQP4 KO mice in both P50 and N95 were shorter than those of WT (t = 5.70 and t = 3.83 respectively, P < 0.01). The mean IOP was significantly (P < 0.05) increased after photocoagulation in AQP4 KO and WT mice compared with pre-photocoagulation [KO post: (14.78 ± 1.80) mm Hg(1 mm Hg = 0.133 kPa) vs KO pre-photocoagulation: (6.61 ± 0.90) mm Hg and WT post: (16.44 ± 1.46) mm Hg vs WT pre-photocoagulation: (7.31 ± 0.98) mm Hg, respectively] with animals under general anesthesia. IOP was lowered mildly but significantly in KO mice when compare with WT mice (t = 3.09, P < 0.05) lasting seven days. IOP was gradually decreased to baseline values at day eight in both of KO and WT mice. Our results indicate that AQP4 null may damage retinal function that can be detected by the measurement of PEGR, a sensitive parameter to reflect the function of RGC.