Activation of satellite glial cells in lumbar dorsal root ganglia contributes to neuropathic pain after spinal nerve ligation.

The role of satellite glial cells (SGCs) of sensory ganglia in chronic pain begins to receive interest. The present study aims to investigate the contribution of SGC activation to the development of neuropathic pain. A neuropathic pain model was established by lumbar 5 spinal nerve ligation (SNL), and glial fibrillary acidic protein (GFAP) was used as a marker of SGC activation. It was found that SGCs were activated in the ipsilateral dorsal root ganglia (DRG) increased significantly as early as 4h following SNL, gradually increased to a peak level at day 7, and then stayed at a high level to the end of the experiment at day 56. SGC activation in the SNL group was significantly higher than that in the sham group at days 1, 3 and 7 after operation. Immunofluorescent double labeling showed that the activated SGCs encircled large, medium-sized and small neurons. The SGCs surrounded the small and medium-sized neurons were preferentially activated in the early phase, but shifted to large diameter neurons as time went on. Continuous infusion of fluorocitrate, a glial metabolism inhibitor, to the affected DRG via mini-osmotic pump for 7d significantly alleviated mechanical allodynia at day 7. These results suggest that SGCs in the DRG were activated after SNL. SGC activation contributed to the early maintenance of neuropathic pain.

Electrophysiological properties of spinal wide dynamic range neurons in neuropathic pain rats following spinal nerve ligation.

OBJECTIVE: The present study aimed to investigate the electrophysiological properties of wide dynamic range (WDR) neurons in spinal dorsal horn of rats with neuropathic pain induced by lumber 5 (L5) spinal nerve ligation (SNL) in a large size of samples. METHODS: Adult Sprague-Dawley rats were divided into normal and SNL groups. Electrophysiological technique was used to record the characteristics of WDR neurons in the spinal dorsal horn. RESULTS: Compared with the WDR neurons in normal rats, the WDR neurons in SNL rats showed an increase in excitability, manifested by an enlargement of the receptive field size, an increase in the proportion of neurons that exhibited spontaneous activities, decreases in the C-response threshold and latency, and an increase in the C-response duration. In addition, the numbers of Aß- and C-fiber-evoked discharges were smaller in SNL rats than in normal rats. CONCLUSION: The excitability of spinal WDR neurons increased in rats with neuropathic pain induced by L5 SNL. The increase in excitability of WDR neurons may contribute to the development of neuropathic pain.