Using neural pathway tracing and immunohistochemical technique, the striato-direct pathway (BDA3 kDa injected into the rat lateral globus pallidus) and striato-indirect pathway (BDA3 kDa injected into the substantia nigra pars reticulata) neurons were specifically labeled, and then subjected to double-labeled immunohistochemistry for mu-OPIOID Receptor (specifically-labeled striatal patch compartment), D1, and D2, respectively. The experimental findings showed that there are no statistically significant differences in the soma diameter and the number of primary dendrites between the striato-direct (substantia nigra pars reticularis) and indirect (globus pallidum externum) neurons labeled retrograde by BDA3 kDa. In addition, these two kinds of projection neurons revealed no obvious coexistence. This evidence indicates that as a highly sensitive neural pathway tracer, BDA could yield reliably and exquisitely detailed labeling of target neurons and synaptic structures. The variance of the morphologic structures and the localization of neurons were not statistically significant between the striato-substantia nigra pars reticularis and the globus pallidum externum projection neurons. Mesencephalic and thalamic neurons correlated with striatal neurons in morphology. Especially the latter which make typical excitatory synaptic contacts with striato-direct and -indirect neurons. Thus, this evidence suggests that thalamic neurons may extensively excite striatal neurons.