Origin of corticospinal neurones evoking monosynaptic excitation in C3-C4 propriospinal neurones in the cat

Intracellular recording was made from propriospinal neurones (PNs) in the C 3-C4 spinal cord segments in the cat (alpha -chloralose anaesthesia). The e ffect of electrical stimulation of corticospinal neurones (CSNs) in the cor tex was investigated. Short C3-C4 PNs were identified by antidromic activat ion of their axons in the ventral horn in C6/C7 and in the lateral reticula r nucleus. Long PNs were antidromically identified from Th12-13. In short P Ns, monosynaptic excitory postsynoptic potentials (EPSPs) were elicited fro m the rostral part of the lateral sigmoid gyrus, the lateral part of the an terior sigmoid gyrus in area 4 gamma and in the adjacent area 6. Two subtyp es of short PNs were identified. PNs of type I received monosynaptic (EPSPs ) from the rostral part of the lateral sigmoid gyrus, the lateral part of t he anterior sigmoid gyrus in area 4 gamma, which is from the same region as disynaptic cortical EPSPs were evoked in forelimb motoneurones. PNs of typ e II received monosynaptic EPSPs from regions slightly more rostrally in th e anterior sigmoid gyrus in area 4 gamma and in the adjacent area 6, which is outside the region from which disynaptic EPSPs could be evoked in foreli mb motoneurones. Long PNs received monosynaptic EPSPs, like the short PNs, by stimulation in the rostral part of the lateral sigmoid gyrus, the latera l part of the anterior sigmoid gyrus in area 4 gamma and in the adjacent ar ea 6. In contrast, the long PNs also received monosynaptic EPSPs from area 3b near the border of area 1. The present results show segregation of the c ortical control to functionally different premotoneuronal systems and sugge st that this control could in part be separated for subtypes of short C3-C4 PNs. (C) 2000 Elsevier Science Ireland Ltd and the Japan Neuroscience Soci ety.