Innervation of substance P neurons by catecholaminergic terminals in the neostriatum.

In this study we tried to establish by the electron microscopic 'mirror technique' whether substance P-like immunoreactive neurons in the neostriatum receive synaptic inputs from catecholaminergic, presumably dopaminergic, nigrostriatal axons. Tyrosine hydroxylase-immunoreactive (TH-IR) axonal boutons were in synaptic contact with the somas and proximal dendrites of SP-IR neostriatal neurons, which are medium in size and have unindented nuclei. This suggests that nigrostriatal dopaminergic neurons monosynaptically influence the strionigral substance P neurons.