Activation of Capsaicin Receptors on the Sciatic Nerve Induces FOS Expression in the Spinal Dorsal Horn of Adult Rats

Abstract

By using immunohistochemical staining for FOS protein in the spinal cord, the role of capsaicin receptors on the sciatic nerve was investigated. After topical application of capsaicin (1%) to the sciatic nerve, FOS-like immunoreactive (FOS-LI) neurons were observed, chiefly in the superficial laminae of the lumbar dorsal horn. Topical application of capsazepine (5%) or lidocaine (2%) to the sciatic nerve for 15 min before the application of capsaicin reduced the number of FOS-LI neurons in the superficial dorsal horn (by 83.2 ± 1.7 and 32.4 ± 1.2%, respectively). One week after pretreatment of the sciatic nerve with colchicine, the number of FOS-LI neurons induced by capsaicin was greatly decreased (by 74.6 ± 1.7%). Given that FOS protein expression after peripheral noxious stimulation is found in a location similar to that in the present study, our results indicate that the capsaicin receptor on the sciatic nerve is involved in the transmission of noxious information.

Pre-treatment with lidocaine suppresses ectopic discharges and attenuates neuropeptide Y and c-Fos expressions in the rat cuneate nucleus following median nerve transection

“…Previous studies reported that injury discharges were accompanied by increased expression of c-Fos LI cells in the spinal cord dorsal horn (Feng et al, 2002;Sun et al, 2004;Stenberg et al, 2005), while lidocaine pre-treatment could inhibit injury discharges and significantly reduce expression of c-Fos-LI cells in the spinal cord dorsal horn at 2 days after injury (Chi et al, 1993;Sun et al, 2004). Interestingly, the lidocaine-induced reduction in the rate of injury discharges and the number of NPY-LI fibers and c-Fos-LI cells in the present study were maintained up for 4 weeks after MNT, while the expression of c-Fos-LI cells in the CN was correlated with the level of NPY reduction.…”

Crosstalk between Spinal Astrocytes and Neurons in Nerve Injury-Induced Neuropathic Pain

“…Fos protein is rapidly expressed in the spinal dorsal horn neurons following noxious peripheral nerve stimulation [21] and correlates well with nociceptive behaviors [19]. Thus, Fos expression is used to identify nociceptive input activated or excited population of neurons [22], [23], [24].…”

Pre-Emptive Treatment of Lidocaine Attenuates Neuropathic Pain and Reduces Pain-Related Biochemical Markers in the Rat Cuneate Nucleus in Median Nerve Chronic Constriction Injury Model

“…This study further showed that the number of c-Fos-LI cells was dose-dependently reduced by lidocaine pre-treatment. Injury discharges have been reported to be implicated in the increase of c-Fos LI cell expression in the spinal cord dorsal horn [32–34], while lidocaine pre-treatment attenuates the discharges to prevent c-Fos induction [21, 34]. …”