Differential Supraspinal Control of Inhibitory and Excitatory Actions from, the FRA to Ascending Spinal Pathways

In the decerebrate state there is an effective tonic inhibition of transmission from the flexor reflex afferents (FRA) to ascending spinal pathways. The release from this tonic control after transverse lesions in the brain stem has been investigated with transmission to ventral spinal pathways. A low pontine lesion releases transmission of inhibitory actions from the FRA whereas a more caudal medullary lesion is required for the release of excitatory actions. This parallels what previously has been found with synaptic actions to motoneurones, and the differential release of inhibition and excitation from the FRA seems to be a general rule. The results are discussed mainly in relation to the functional significance of the excitatory and inhibitory actions from the FRA to ascending spinal pathways.