[Corticofugal influences on the reticulospinal neurons of gigantocellular nucleus in cats].

Stimulation of the motor cortex evoked excitatory and inhibitory PSP in reticulospinal neurons of the cat gigantocellular nucleus. EPSP were recorded in 94.3% of the investigated neurons and IPSP in 5.7%. Analysis of the presynaptic pathways showed that 77.4% of EPSPs appeared through monosynaptic and 22.6% through polysynaptic corticoreticular connections. According to latency, duration and rise time all monosynaptic EPSP were divided into two groups (fast and slow). Obviously, fast EPSPs are generated by fast corticobulbar fibres and slow ones by slow fibres. IPSP were recorded in neurons which were also inhibited by stimulation of the ventral funiculi of the spinal cord. It is suggested that motor cortical signals can be transmitted to the spinal cord through both mono- and polysynaptic connections of the fast and slow pyramidal neurons with reticulospinal neurons.