[Interneuronal reactions of the ventral horn to rhythmic activation of skin and muscle afferents].

Spike and slow postsynaptic activities of the cat spinal interneurons (IN) of intermediate and motor regions (L6, 7) evoked with rhythmic stimulation of the hindlimb skin and muscle afferents, were intra--and extracellularly recorded. The pattern of responses was not constant: the same IN could respond in both "tonic" and "phasic" ways to stimulation of different inputs. The pattern seems to depend on synaptic organization of respective input. Two main inhibitory mechanisms (presynaptic inhibition and postdischarge hyperpolarization in IN) are discussed. Different effects evoked by activation of the same afferent input in various IN suggest that IN of segmental intrinsic system do not constitute a homogeneous population but belong to differentiated systems.