Differential Synaptic Input to External Globus Pallidus Neuronal Subpopulations In Vivo

Summary The rodent external Globus Pallidus (GPe) contains two main neuronal subpopulations, prototypic and arkypallidal cells, which differ in their cellular properties. Their functional synaptic connectivity is, however, largely unknown. Here, we studied the membrane properties and synaptic inputs to these subpopulations in the mouse GPe. We obtained in vivo whole-cell recordings from identified GPe neurons and used optogenetic stimulation to dissect their afferent inputs from the striatum and subthalamic nucleus (STN). All GPe neurons received barrages of excitatory and inhibitory input during slow wave activity. The modulation of their activity was cell-type specific and shaped by their respective membrane properties and afferent inputs. Both GPe subpopulations received synaptic input from STN and striatal projection neurons (MSNs). STN and indirect pathway MSNs strongly targeted prototypic cells while direct pathway MSNs selectively inhibited arkypallidal cells. We show that GPe subtypes are differently embedded in the basal ganglia network, supporting distinct functional roles.