Session 3E: Innervation of Pathway-Specific Striatal Spiny Projection Neurons by Npas1+ Neurons of the External Globus Pallidus

The external globus pallidus (GPe) and dorsal striatum are two structures of the basal ganglia, which are a set of subcortical, movement related nuclei in the brain. The GPe projects into the striatum and provides an inhibitory input. However, the magnitude of this input and locations of pallidostriatal synapses have not yet been described. Because the GPe has been shown to have a role in motor function and dysfunction, its input to the striatum, which effectively begins basal ganglia circuitry, is of interest. By examining the anatomical input of Npas1+ GPe axons to striatal cells, the majority of which are spiny projection neurons (SPNs), we determined general pallidostriatal pathway characteristics, and then compared the GPe input to direct-pathway SPNs (dSPNs) and indirect-pathway SPNs (iSPNs). We found that the GPe-iSPN contacts occur closer to the somatic body than GPe-dSPN inputs. Contacts closer to the somatic body elicit stronger inhibition. We also tested if the nature of the input changes in a Parkinson\u27s disease (PD) model. Although GPe activity has been shown to increase in PD, GPe-SPN contacts did not shift. We presume that the observed change in the pallidostriatal pathway following dopamine depletion must be a result of some other mechanism