[Changes in inhibitory responses in the spinal cord of the cat induced by stimulation of suprasegmental structures during rhythmic stimulation of the locus coeruleus].

Effects of rhythmic locus coeruleus stimulation on spinal reactions evoked by cortico-, reticulo- and vestibulospinal influences were studied in anesthetized decerebellized cats. Two-component inhibitory reactions in extensor and excitatory-inhibitory reactions in flexor motoneurons were found after the stimulation of the motor cortex or the medullary reticular formation. The locus coeruleus stimulation depressed the late component of responses in both group of motoneurons but had a less influence on the early inhibitory and excitatory components. No changes were observed in reactions evoked by vestibulospinal influences in the extensor and flexor motoneurons. Mechanisms of descending influences of locus coeruleus on spinal reactions evoked by primary afferents and supraspinal structures are discussed.