Neurosciencc Letters, 75 (1987) 253 258 253 Elsevier Scicntitic Publishers Ireland Ltd. NSL 04496 Response of lumbar spinocervical tract cells to natural and electrical stimulation of the hindlimb footpads in cats W.A.A. Kunze, P. Wilson and P.J. Snow Department o[ Amttomy, ( "niversi O' o[ Queenshmd, St. Lucia, Qld. t A u,~tralia ) (Received 2 April 1986: Revised version received I November 1986; Accepted 2 December I986) Key wordy." Cat; Spinocervical tract; Dorsal horn: Receptive field: Ilorseradish pcroxidasc: Afferent liber Extraccllular and intracellular recordings were made from antidromically identilied spinoccrvical tract (SCT) cells in the medial part of the lumbosacral dorsal horn in anesthetized cats. The Io~ threshold mechanoreceplivc ticlds (RFs) of 18 cells were mapped during extracellular recording, and for 15 the R F included an area of glabrous skin. lntracellular recordings were made from 6 of these during electrical microstimulation of glabrous skin and all showed excitatory postsynaptic potentials at latencies consistenl with conduction over group II primary afferent fibers. The distance fronl lhc medial border of Ihe dorsal horn of the recording loci of 12 cells. 4 of which were injected with horseradish pcroxidase, was measured. 11 is concluded that some medially situated S('T cells receive excitatory input from low threshold group 11 primary afferent fibers from glabrous skin. Several workers have noted that the most medially placed cells in the dorsal horn of the lumbosacral enlargement of the cat spinal cord have excitatory low threshold mechanoreceptive fields (RFs) which encompass part of the glabrous skin of the hindlimb pads [2, 3, 5, 18]. Usually no attempt has been made to identify the axonal projections of these cells. On the basis of recording from identified spinocervical tract (SCT) axons within the dorsolateral funiculus in the cat, Brown and Franz [6] con- cluded that SCT neurons were not excited by light mechanical stimulation of gla- brous skin (see also refs. 4 and 5). In contrast, recordings from identified postsynaptic dorsal column neurons in the cat have shown that some of these are clearly excited by stimulation of the skin of the pads [1, 7]. In a recent, detailed study of the somato- tophic organization of the cat's lumbosacral dorsal horn [t8] we encountered what we believe to be clear indications that some antidromically identified SCT cells located in the most medial part of the dorsal horn are also excited by light tactile stimulation of glabrous skin. Corre,s?9ondence." P.J. Snow, Department of Anatomy, University of Queensland, St. Lucia, Qld. 4067, Australia. 0304-3940;87 'S 03.50 (~ 1987 Elsevier Scientific Publishers Ireland Lid.