Brainstem relay of disynaptic pyramidal EPSPs to neck motoneurons in the cat.

A short train of stimuli delivered to the contralateral pyramid evoked EPSPs with disynaptic latencies in neck motoneurons. After a transection of the pyramid at the obex, stimulation rostral to the lesion still evoked disynaptic EPSPs. Stimulation of the pyramid rostral to a transection at the level of the trapezoid body did not produce synaptic effects. It is suggested that the disynaptic EPSPs in neck motoneurons from the contralateral pyramid are mediated by medullary reticulospinal neurons.