The axonal arborization of single nigrostriatal neurons in rats

Neurons of the substantia nigra pars compacta (SNc) were iontophoretically injected with biotin dextran and their anterogradely labeled axons individu ally reconstructed from serial sagittal sections. Most nigrostriatal axons travelled directly to the striatum, where they branched abundantly. Other a xons arborized profusely in various extrastriatal structures, including the globus pallidus, the entopeduncular and subthalamic nuclei, and branched o nly sparsely in the striatum. This heterogeneous organization of the nigros triatal projection allows single SNc neurons to influence differently stria tal neurons and to act directly upon extrastriatal components of the basal ganglia via a highly patterned set of collaterals. (C) 1999 Elsevier Scienc e B.V. All rights reserved.