Long C3-C5 propriospinal neurones in the cat.

Intracellular recording was made in the C3-C5 segments of cats from cells identified as long propriospinal neurones (PNs) by antidromic activation from the lower thoracic segments. The cell bodies were in laminae VII and VIII and their ventrally located axons were either uncrossed or crossed. Stimulation of higher motor centres revealed monosynaptic excitatory postsynaptic potentials (EPSPs) from cortico-, rubro-, tecto-, reticulo-, interstitio-, fastigio- and trigeminospinal fibres. Monosynaptic inhibitory postsynaptic potentials (IPSPs) were evoked from reticulospinal fibres. These PSPs were in addition to the separately described effects from the vestibular nuclei. Monosynaptic EPSPs were also evoked in some cells from neck or forelimb afferents and disynaptic EPSPs or IPSPs from forelimb afferents.