Incidence of mononeuropathy in rats is influenced by pre-emptive alteration of spinal excitability.

Both clinical and experimental data support the notion that the development of neuropathic pain is related to the state of excitability at the time of nerve injury. The present study was performed to investigate whether altering spinal excitability immediately before creation of a chronic constriction nerve injury in rats can influence the incidence of tactile hypersensitivity ('allodynia') by using pre-emptive: (1) intrathecal injection of a GABAB agonist or antagonists; (2) intrathecal lidocaine; or (3) C-fibre activation by electric stimulation. The incidence of tactile hypersensitivity was significantly reduced by the GABA(B) agonist baclofen while it was markedly enhanced by the administration of the GABA(B) antagonists 5-AVA and CGP 55845, as well as by C-fibre stimulation. Intrathecal administration of lidocaine did not influence the incidence of hypersensitivity. The results suggest that GABAergic mechanisms play an important role in the development of tactile hypersensitivity, and suggest that GABA(B) receptor agonists may be used as pre-emptive treatment to prevent the development of postinjury neuropathic pain.