Figure 9.

Schematic diagram of an immature CNS neuron (left, high [Cl⁻]_i) and an adult CNS neuron (right, low [Cl⁻]_i). Opening GABA_AR leads to Cl⁻ exit and depolarization in immature neurons, whereas it causes Cl⁻ entry and hyperpolarization in the adult neuron. The switch from excitatory effect of GABA to inhibition induced by modulation in KCC2 and NKCC1 expression during development is reversed after SCI. We suggest that this change in chloride cotransporter expression that is involved in the development of hyperreflexia after SCI is reverted by exercise.