Non-dopaminergic neurons in the substantia nigra project to the reticular formation around the trigeminal motor nucleus in the rat.
The dorsolateral part of the substantia nigra (SN) of the rat was observed to send projection fibers to the reticular formation (RF) around the trigeminal motor nucleus (Vm), bilaterally with a clear-cut ipsilateral dominance, by the anterograde and retrograde tracing techniques with PHA-L and WGA-HRP. A combination of retrograde tracing and immunohistochemistry for tyrosine hydroxylase (TH) revealed that no SN neurons sending their axons to the RF around the Vm showed TH-like immunoreactivity.