Attenuation of AMPA receptor activity improves motor skills in a mouse model of juvenile Batten disease

Abstract

Juvenile Batten disease, caused by mutations in the CLN3 gene, is a fatal, incurable neurodegenerative disorder in children. The Cln3-loss-of-function (Cln3(Deltaex1-6)) mouse model of the disease exhibits many characteristic pathological features of the human disorder including a deficit in motor skills. Our recent findings [Kovács, A.D., Weimer, J.M., Pearce, D.A., 2006. Selectively increased sensitivity of cerebellar granule cells to AMPA receptor-mediated excitotoxicity in a mouse model of Batten disease. Neurobiol. Dis. 22, 575-585] suggested that the neurological deficit in the Cln3(Deltaex1-6) mouse model of the disease might result from an abnormally increased AMPA receptor activity in the cerebellum. Therefore, we tested if administration of low doses of an AMPA receptor antagonist, that attenuate AMPA receptor function but avoid a toxic, complete blockade of the receptor, have beneficial effects in Cln3(Deltaex1-6) mice. Here we show that attenuation of AMPA receptor activity by a single intraperitoneal injection of the non-competitive AMPA antagonist, EGIS-8332 (1 mg/kg), significantly improves the motor skills of Cln3(Deltaex1-6) mice. Our results provide a new, promising therapeutic approach for juvenile Batten disease.

Fig. 1. A single intraperitoneal injection of a selective, non-competitive AMPA receptor antagonist significantly improves the motor skills in the Cln3-loss-of function (Cln3^Δex1-6) mouse model of juvenile Batten disease

An accelerating rotarod was used to measure motor skills of one-month-old Cln3^Δex1-6 and wild type (WT) mice. Two hours and thirty minutes after the end of the Pre-treatment test, animals were intraperitoneally injected with the selective, non-competitive AMPA antagonist, EGIS-8332, in the indicated doses. Control mice were injected with the vehicle of the drug (20 mM HCl containing 10% DMSO). Thirty minutes after the injection, the Post-treatment test was performed. The latencies to fall from the rotating rod during the Pre- and Post-treatment testing periods were calculated for each mouse. Columns and bars represent mean ± S.E.M. of the time (s) mice were able to stay on the rotating rod. All data sets passed the normality test (alpha level 0.05), and therefore, two-tailed t-tests and one-way ANOVA were applied in the statistical analysis. (A) Impaired motor skills in one-month-old Cln3^Δex1-6 mice. Combined Pre-treatment test results of 19 WT and 28 Cln3^Δex1-6 mice are shown. *p=0.0000071, unpaired t-test (B) The selective, non-competitive AMPA receptor antagonist, EGIS-8332, dose-dependently affects the motor skills of one-month-old Cln3^Δex1-6 mice (n=4-6). The lowest, 1 mg/kg, dose significantly improved motor skills: **p=0.0066, paired t-test: Post-treatment vs. Pre-treatment; ^#p=0.0272, oneway ANOVA followed by Bonferroni's test for comparison of Post-treatment times (Control vs. 1, 3 and 10 mg/kg). (C) A single intraperitoneal injection of EGIS-8332 at a low dose (1 mg/kg) significantly improves the motor skills of Cln3^Δex1-6 mice (Control: n=11; 1 mg/kg EGIS-8332: n=17). Empty columns: Pre-treatment test results; grey columns: Post-treatment test results. Pre- vs. Post-treatment: paired t-test, p=0.00004; Comparison of Post-treatment results: unpaired t-test, p=0.0036. (D) A single intraperitoneal injection of EGIS-8332 at a low dose (1 mg/kg) does not affect the motor skills of WT mice (Control: n=9; 1 mg/kg EGIS-8332: n=10). Empty columns: Pre-treatment test results; grey columns: Post-treatment test results. Pre- vs. Post-treatment: paired t-test, p=0.0052 for Control and p=0.0288 for 1 mg/kg EGIS-8332; Comparison of Post-treatment results: unpaired t-test, p=0.3567, not significant.