Response of lumbar spinocervical tract cells to natural and electrical stimulation of the hindlimb footpads in cats

Extracellular and intracellular recordings were made from antidromically identified spinocervical tract (SCT) cells in the medial part of the lumbosacral dorsal horn in anesthetized cats. The low threshold mechanoreceptive fields (RFs) of 18 cells were mapped during extracellular recording, and for 15 the RF included an area of glabrous skin. Intracellular recordings were made from 6 of these during electrical microstimulation of glabrous skin and all showed excitatory postsynaptic potentials at latencies consistent with conduction over group II primary afferent fibers. The distance from the medial border of the dorsal horn of the recording loci of 12 cells, 4 of which were injected with horseradish peroxidase, was measured. It is concluded that some medially situated SCT cells receive excitatory input from low threshold group II primary afferent fibers from glabrous skin.