Journal of neurophysiology
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1. Extracellular single-unit recordings have been made from 295 dorsal horn neurons in the lumbar enlargement of rat spinal cord; 191 neurons in 20 rats with an experimental peripheral neuropathy, and 104 in 10 sham-operated rats. Recordings were made 9-11 days after inducing the neuropathy by tying four loose ligatures around the sciatic nerve in the nerve-injured rats or performing a sham procedure in the sham-operated rats. 2. ⋯ However, there was a group of neurons in the nerve-injured rats that had low thresholds, failed to encode stimulus intensity, and did not have a C-fiber input. 5. There were significantly fewer neurons excited by low-intensity stimulation of the skin in the nerve-injured (24%; 43/180) than in the sham-operated rats (71%; 74/104). Measurements of mechanical threshold with von Frey hairs showed that, although the mean threshold did not change, none of the cells tested in the nerve-injured animals had thresholds < 12 mN, whereas the lowest threshold recorded in the sham-operated animals was 0.2 mN.(ABSTRACT TRUNCATED AT 400 WORDS)