THE EFFECTS OF SWIM TRAINING ON SYNAPTIC PLASTICITY AND EXCITABILITY IN SOMATOSENSORY CORTEX IN A MOUSE MODEL OF AMYOTROPHIC LATERAL SCLEROSIS

Somatosensory cortex hyperexcitability is observed during the presymptomatic stage of amyotrophic lateral sclerosis (ALS). We examined synaptic plasticity in females of a mouse model of ALS, focusing on the B2 barrel of the somatosensory cortex. We measured the density of excitatory and inhibitory synapses and analysed morphological changes of dendritic spines. Transgenic mice, B6SJL-Tg (SOD1G93A) 1Gur/J, were used as the ALS model, and wild type (WT) mice B6SJL/F1, served as controls. ALS mice were divided and analysed before the onset of the disease, at the onset, and at the terminal stage with, and without swim training. We analysed and quantified the density of excitatory and inhibitory synapses and their ratios (E/I) using serial electron micrographs. We found an increase in the total density of excitatory synapses in the ALS before group and a decline in the number of excitatory synapses in the ALS group after swim training. Here, for the first time, we show an increase in the density of inhibitory synapses in the ALS onset group, which suggests a compensatory mechanism to prevent or balance the hyperexcitability of neurons in the somatosensory cortex. The E/I ratio was lowered after swim training in the ALS trained group, indicating a shift toward decreased cortical excitation. Our data showed that swim training in female ALS mice is associated with decreased hyperexcitability and E/I ratio. These findings indicate the importance of swim training as a potential therapeutic approach with possible applications in ALS patients.