title: Postinhibitory rebound facilitation of the extension reflex in the high spinal cat.
abstract: Neural mechanisms of the reflex rebound of the hindlimb were studied in the high spinalized cat. After the animal had recovered from spinal shock, a light touch-pressure on the foot pad elicited a rebound extension reflex of the ipsilateral hindlimb. Excitability changes in hindlimb motor nuclei during the rebound phenomenon were examined by recording test monosynaptic reflexes (MSR). During touch-pressure stimulation, flexors such as the biceps femoris and tibialis anterior were facilitated, while extensors such as the gastrocnemius and quadriceps femoris were inhibited. After cessation of a stimulus, extensor MSRs showed a rebound facilitation which lasted for a few seconds. The greater the preceding suppression of MSR, the greater the rebound facilitation. Membrane potential changes induced in extensor motoneurons by touch-pressure were investigated by intracellular recordings. In most of the motoneurons tested (21/24), a clear membrane hyperpolarization was observed during stimulation and was followed by a rebound firing on cesstion of stimulation. Possible mechanisms underlying the rebound extension reflex were discussed.
mesh_terms: D000818:Animals; D002415:Cats; D003655:Decerebrate State / Q000503:physiopathology*; D004576:Electromyography; D006614:Hindlimb / Q000502:physiology; D008564:Membrane Potentials; D009046:Motor Neurons / Q000502:physiology; D012018:Reflex / Q000502:physiology*