3,5-Dimethyladamantan-1-amine Restores Short-term Synaptic Plasticity by Changing Function of Excitatory Amino Acid Transporters in Mouse Model of Spinocerebellar Ataxia Type 1

Introduction. Memantine is an agent that used for treatment of Alzheimer's type dementia. Memantine considerably reduces the effects of neurodegeneration, may potentially slow down the neurodegenerative changes in the cerebellum and may act as treatment of choice for spinocerebellar ataxia type 1 (SCA 1). Our objective was to study molecular mechanisms of the short-term synaptic plasticity improvement associated with long-term memantine use in SCA 1 transgenic mice. Materials and methods. The experiments were performed on 12-week-old CD1 mice. We created a mouse model of cerebellar astrogliosis after expression of mutant ataxin-1 (ATXN1[Q85]) in the Bergmann glia (BG). To model the astrocyte-mediated neurodegeneration in the cerebellum, the mice were injected with LVV GFAP-Flag-ATXN1[Q85] lentiviral vector (LVV) constructs intracortically. Some of the mice received 0.35 mg/kg memantine dissolved in drink water once daily for 9 weeks. The control animals were administered LVV GFAP-ATXN1[Q2]-Flag. Changes of the excitatory postsynaptic currents amplitudes from Purkinje cells (PC) were recorded by patch clamp. Expression of anti-EAAT1 in the cerebellar cortex was assessed using immunohistochemistry. Results. The reactive glia of the cerebellar cortex in SCA1 mice is characterized by a decrease in the immunoreactivity of anti-EAAT1, while chronic memantine use restores this capacity. The decay time of the excitatory postsynaptic current amplitude in the parallel fiber-Purkinje cell (PF-PC) synapses of the SCA1 mice is considerably longer, which indicates the slowing of glutamate reuptake and EAAT1 dysfunction. The prolonged presence of increased neurotransmitter levels in the synaptic cleft facilitates activation of the mGluR1 signaling and restoration of mGluR1-dependent synaptic plasticity in Purkinje cells of the SCA1 mice. Conclusions. The slowing of neurotransmitter reuptake associated with long-term memantine treatment improves mGluR1-dependent short-term synaptic plasticity of the Purkinje cells in the SCA1 mice. Restoration of synaptic plasticity in these animals may underlie partial reduction of ataxic syndrome.