GAT-3 Dysfunction Generates Tonic Inhibition in External Globus Pallidus Neurons in Parkinsonian Rodents

Abstract

Summary: The external globus pallidus (GP) is a key GABAergic hub in the basal ganglia (BG) circuitry, a neuronal network involved in motor control. In Parkinson’s disease (PD), the rate and pattern of activity of GP neurons are profoundly altered and contribute to the motor symptoms of the disease. In rodent models of PD, the striato-pallidal pathway is hyperactive, and extracellular GABA concentrations are abnormally elevated in the GP, supporting the hypothesis of an alteration of neuronal and/or glial clearance of GABA. Here, we discovered the existence of persistent GABAergic tonic inhibition in GP neurons of dopamine-depleted (DD) rodent models. We showed that glial GAT-3 transporters are downregulated while neuronal GAT-1 function remains normal in DD rodents. Finally, we showed that blocking GAT-3 activity in vivo alters the motor coordination of control rodents, suggesting that GABAergic tonic inhibition in the GP contributes to the pathophysiology of PD. : The globus pallidus (GP) is a key basal ganglia nucleus involved in motor control. In Parkinson’s disease, the cellular mechanisms underlying GP neuron hypoactivity are poorly understood. Chazalon et al. find that glial GABA transporters are downregulated in parkinsonian rodents, leading to aberrant GABAergic inhibition in the GP and motor coordination impairment. Keywords: tonic inhibition, basal ganglia, extrasynaptic GABAA receptors, GABA transporters, electrophysiology