[Effect of rhythmic stimulation of the locus coeruleus on spinal inhibition induced by activation of flexor reflex afferents in the cat].

Locus coeruleus rhythmic stimulation of 40/s frequency and 50-150 micro A current intensity diminished the inhibitory action from flexor reflex afferents on extensor monosynaptic reflexes in anaesthetized decerebellized cats. Such an effect appeared 600 ms after and reached maximum 1500-1700 ms after the locus coeruleus stimulation. The depression of inhibition was maintained during 2-3 s after cessation of the stimulation. No effect was observed when locus coeruleus was stimulated by a single stimulus or by a short high-frequency pulse train of the same current strength. An increase of the stimulation intensity evoked activation of neighbouring structures. The advantages of the rhythmic stimulation for revealing the influences of slow conducting pathways are discussed.