| Abstract: | Parallel intracellular recordings of potentials in primary afferent fibers (in the region of their entry into the spinal cord) and motoneurons were made in experiments on an isolated perfused preparation of frog spinal cord preserving its connections with hind limb nerves. It was shown by injection of horseradish peroxidase through a microelectrode inserted into the fiber that fast-conducting cutaneous, tendon, and muscular afferents connected polysynaptically with motoneurons reach only the upper or middle third of the dorsal horn. Terminal branches of these fibers are characterized by numerous short terminal twigs given off at short distances apart from larger collaterals. Terminal boutons and en passant contacts, stained with horseradish peroxidase, were found on bodies of interneurons. In some cases, trans-synaptic staining of interneurons was found to take place. It is suggested that peroxidase-labeled interneurons form axo-axonal synapses with primary afferents.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 14, No. 6, pp. 615–621, November–December, 1982. |
