[Intracellular horseradish peroxidase injection study of connections between primary afferents and spinal cord motor neurons in the frog].

Simultaneous intracellular penetration of a frog motoneuron and a single primary afferent fibre monosynaptically connected with it was used for potential recording followed by HRP injection. Subsequent histological reconstruction of labelled motoneurons and their afferents revealed numerous contacts between them. These contacts were found both on the motoneuronal soma and dendrites, being most numerous in the proximal parts of dendrites and in the second-third-order branches. Recurrent collaterals of motoneuron axons and their contacts with dendrites were found.