On the function of the fast long spinal inhibitory pathway from forelimb afferents to flexor digitorum longus motoneurones in cats and dogs.

In high spinal cats an oligosynaptic inhibitory reflex pathway from forelimb afferents specifically to hindlimb flexor digitorum and hallucis longus (FDL) motoneurones has been established. The present investigation yielded further results for a functional interpretation of this specific pathway. The IPSPs in FDL motoneurones could be evoked by weak innocuous mechanical stimuli to the forepaw. During fictive locomotion they were predominantly transmitted during the active phase of the FDL i.e., during the extension phase. With monosynaptic reflex testing a similar propriospinal inhibition of FDL motoneurones was demonstrated in dogs. It is assumed, that this propriospinal inhibition of FDL motoneurones implies a mechanism for preventing a plantar flexion of the toes during periods of the hindlimb extension phase.