Journal of Neurophysiology, Vol 69, Issue 6 2072-2085, Copyright © 1993 by APS

ARTICLES

An electrophysiological study of dorsal horn neurons in the spinal cord of rats with an experimental peripheral neuropathy

J. M. Laird and G. J. Bennett
Neurobiology and Anesthesiology Branch, National Institute of Dental Research, NIH, Bethesda, Maryland 20892.

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. A survey of the general properties of all neurons encountered was made in the 10 sham-operated rats (104 neurons) and compared with those seen in 17 of the nerve-injured animals (180 neurons). The vast majority (87%; 156/180) of neurons recorded in the nerve-injured animals showed abnormal characteristics; these included responses to very gentle mechanical stimulation of the nerve-injury site and to manipulations that resulted in movement of this site such as extension of the leg and probing of the skin and muscle of the thigh (53%), absence of detectable peripheral receptive fields (RFs; 56%), and very high spontaneous activity (7%). In the sham-operated rats none of the neurons recorded could be activated by gentle mechanical stimulation of the sciatic nerve, and only 6% had no detectable peripheral RF. 3. In the nerve-injured animals, 31% (55/180) of cells had both a peripheral RF, and a response to gentle mechanical stimulation of the nerve-injury site. All cells of this type tested (n = 5) showed very prolonged responses (up to 10 min long) to 15 s pinch stimuli applied to the RF and to 15 s gentle tapping of the injury site. The majority of cells in this group were excited by noxious stimuli (71%; 39/55) and had C-fiber inputs (60%; 33/55). 4. The mean threshold temperatures for evoking responses to heat stimuli in cells tested in nerve-injured rats and in sham-operated animals were not different. 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)

This article has been cited by other articles:

				K. Saito, S. Hitomi, I. Suzuki, Y. Masuda, J. Kitagawa, Y. Tsuboi, M. Kondo, B. J. Sessle, and K. Iwata Modulation of Trigeminal Spinal Subnucleus Caudalis Neuronal Activity Following Regeneration of Transected Inferior Alveolar Nerve in Rats J Neurophysiol, May 1, 2008; 99(5): 2251 - 2263. [Abstract] [Full Text] [PDF]

				V. B. Lu, K. Ballanyi, W. F. Colmers, and P. A. Smith Neuron type-specific effects of brain-derived neurotrophic factor in rat superficial dorsal horn and their relevance to 'central sensitization' J. Physiol., October 15, 2007; 584(2): 543 - 563. [Abstract] [Full Text] [PDF]

				C. Liu and J. M. Walker Effects of a Cannabinoid Agonist on Spinal Nociceptive Neurons in a Rodent Model of Neuropathic Pain J Neurophysiol, December 1, 2006; 96(6): 2984 - 2994. [Abstract] [Full Text] [PDF]

				M. Devor Centralization, Central Sensitization and Neuropathic Pain. Focus on "Sciatic Chronic Constriction Injury Produces Cell-Type-Specific Changes in the Electrophysiological Properties of Rat Substantia Gelatinosa Neurons" J Neurophysiol, August 1, 2006; 96(2): 522 - 523. [Full Text] [PDF]

				S. Balasubramanyan, P. L. Stemkowski, M. J. Stebbing, and P. A. Smith Sciatic Chronic Constriction Injury Produces Cell-Type-Specific Changes in the Electrophysiological Properties of Rat Substantia Gelatinosa Neurons J Neurophysiol, August 1, 2006; 96(2): 579 - 590. [Abstract] [Full Text] [PDF]

				B. Liu and J. C. Eisenach Hyperexcitability of Axotomized and Neighboring Unaxotomized Sensory Neurons Is Reduced Days After Perineural Clonidine at the Site of Injury J Neurophysiol, November 1, 2005; 94(5): 3159 - 3167. [Abstract] [Full Text] [PDF]

				J. H. Brock, A. Elste, and G. W. Huntley Distribution and Injury-Induced Plasticity of Cadherins in Relationship to Identified Synaptic Circuitry in Adult Rat Spinal Cord J. Neurosci., October 6, 2004; 24(40): 8806 - 8817. [Abstract] [Full Text] [PDF]

				J.-X. Hao, R. C. Kupers, and X.-J. Xu Response Characteristics of Spinal Cord Dorsal Horn Neurons in Chronic Allodynic Rats After Spinal Cord Injury J Neurophysiol, September 1, 2004; 92(3): 1391 - 1399. [Abstract] [Full Text] [PDF]

				P. J. Siddall and M. J. Cousins Persistent Pain as a Disease Entity: Implications for Clinical Management Anesth. Analg., August 1, 2004; 99(2): 510 - 520. [Abstract] [Full Text] [PDF]

				B. C. Hains, C. Y. Saab, J. P. Klein, M. J. Craner, and S. G. Waxman Altered Sodium Channel Expression in Second-Order Spinal Sensory Neurons Contributes to Pain after Peripheral Nerve Injury J. Neurosci., May 19, 2004; 24(20): 4832 - 4839. [Abstract] [Full Text] [PDF]

				V. Galhardo, A. V. Apkarian, and D. Lima Peripheral Inflammation Increases the Functional Coherency of Spinal Responses to Tactile but not Nociceptive Stimulation J Neurophysiol, October 1, 2002; 88(4): 2096 - 2103. [Abstract] [Full Text] [PDF]

				S.-R. Chen and H.-L. Pan Hypersensitivity of Spinothalamic Tract Neurons Associated With Diabetic Neuropathic Pain in Rats J Neurophysiol, June 1, 2002; 87(6): 2726 - 2733. [Abstract] [Full Text] [PDF]

				K. Iwata, T. Imai, Y. Tsuboi, A. Tashiro, A. Ogawa, T. Morimoto, Y. Masuda, Y. Tachibana, and J. Hu Alteration of Medullary Dorsal Horn Neuronal Activity Following Inferior Alveolar Nerve Transection in Rats J Neurophysiol, December 1, 2001; 86(6): 2868 - 2877. [Abstract] [Full Text] [PDF]

				E. Eisenberg, Y. Lurie, C. Braker, D. Daoud, and A. Ishay Lamotrigine reduces painful diabetic neuropathy: A randomized, controlled study Neurology, August 14, 2001; 57(3): 505 - 509. [Abstract] [Full Text] [PDF]

				D. Bridges, S. W. N. Thompson, and A. S. C. Rice Mechanisms of neuropathic pain Br. J. Anaesth., July 1, 2001; 87(1): 12 - 26. [Abstract] [Full Text] [PDF]

				V. A. Mitchell, D. M. White, and M. J. Cousins The Long-Term Effect of Epidural Administration of Butamben Suspension on Nerve Injury-Induced Allodynia in Rats Anesth. Analg., October 1, 1999; 89(4): 989 - 989. [Abstract] [Full Text] [PDF]

				V. Morisset and F. Nagy Ionic Basis for Plateau Potentials in Deep Dorsal Horn Neurons of the Rat Spinal Cord J. Neurosci., September 1, 1999; 19(17): 7309 - 7316. [Abstract] [Full Text] [PDF]

				R. Baron, Y. Baron, E. Disbrow, and T. P. L. Roberts Brain processing of capsaicin-induced secondary hyperalgesia: A functional MRI study Neurology, August 1, 1999; 53(3): 548 - 548. [Abstract] [Full Text]