Comparative Analysis of the Axonal Collateralization Patterns of Basal Ganglia Output Nuclei in the Rat

Axonal collateralization is a major organizational feature of basal ganglia circuits. Single-axon tracing techniques reveal the full collateralization patterns of individual axons, providing key connectional information about target diversity. Previous studies from our group have analyzed the axonal branching patterns of two output nuclei of the basal ganglia in the rat, the ventral pallidum (VP) and the substantia nigra pars reticulata (SNr). In this review we compare individual VP and SNr neurons, highlighting common features and unique characteristics, which may contribute to a deeper understanding of their respective connections and function. We additionally outline parallels with the entopeduncular nucleus and the globus pallidus that may help develop a more comprehensive understanding of basal ganglia organization.