Changes in tactile stimuli-induced behavior and c-Fos expression in the superficial dorsal horn and in parabrachial nuclei after sciatic nerve crush

• Published in: Journal of comparative neurology (1911) Vol. 428; no. 1; pp. 45 - 61
• Main Authors: Bester, Hervé, Beggs, Simon, Woolf, Clifford J.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 04.12.2000
• Subjects: allodynia; Animals; Cell Count; dorsal horn; Male; Mesencephalon - metabolism; Nerve Crush - adverse effects; nerve injury; Nerve Regeneration - physiology; Neuronal Plasticity - physiology; Nociceptors - cytology; Nociceptors - metabolism; pain; Pain - etiology; Pain - pathology; Pain - physiopathology; pain, plasticity; parabrachial area; parabrachial nucleus; Peripheral Nervous System Diseases - etiology; Peripheral Nervous System Diseases - pathology; Peripheral Nervous System Diseases - physiopathology; Physical Stimulation; plasticity; Pons - metabolism; Posterior Horn Cells - metabolism; Proto-Oncogene Proteins c-fos - metabolism; Rats; Rats, Sprague-Dawley; Touch - physiology
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/1096-9861(20001204)428:1<45::AID-CNE5>3.0.CO;2-A

Neurons in the superficial laminae of the dorsal horn are dominated by input from peripheral nociceptors. Following peripheral nerve injury, low threshold mechanoreceptive Aβ‐fibers sprout from their normal termination site in laminae III/IV into laminae I–II and this structural reorganization may contribute to neuropathic tactile pain hypersensitivity. We have now investigated whether a sciatic nerve crush injury alters the behavioral response in rats to tactile stimuli and whether this is associated with a change in the pattern of c‐Fos expression in the dorsal horn and the parabrachial area of the brainstem. Sciatic nerve crush resulted in a patchy but marked tactile allodynia manifesting first at 3 weeks and persisting for up to 52 weeks. C‐Fos expression in the dorsal horn and parabrachial region was never observed on brushing the skin of the sciatic nerve territory in animals with intact nerves, but was found after sciatic nerve crush with peripheral regeneration. We conclude that after nerve injury, low threshold mechanoreceptor fibers may play a major role in producing pain‐related behavior by activating normally nociceptive‐specific regions of the central nervous system such as the superficial laminae of the dorsal horn and the parabrachial area. J. Comp. Neurol. 428:45–61, 2000. © 2000 Wiley‐Liss, Inc.