Effects of gaboxadol on the pain and spinal astrocyte activation of rats with neuropathological pain

Abstract

Objective To explore the effects of subcutaneous injection of γ aminobutyric acid(GABA) A receptor agonist gaboxadol for the pain threshold of rats with neuropathological pain(NP) and the activation of spinal astrocytes. Methods A NP model was established in rats through chronic constriction injury (CCI) of the sciatic nerve. Thirty-six male SD rats were randomized into three groups(n=12): a sham group (group S), a CCI group (group C) and a CCI+gaboxadol group (group G). Then, normal saline or 10 mg/kg gaboxadol was subcutaneously injected in group S, group C or group G respectively, once a day, from Days 10 to 14 after operation. 8 rats were randomly selected in each group, and paw withdrawal mechanical threshold(PWMT) was measured one day before operation and on day 3 and 10 after operation, and 0.5, 1, 2, 4, 8, 12 h after final injection. 4 rats were selected in each group, and they were killed sacrificed 2 h after final injection and the expression of astrocytes in the spinal cord was measured by immunofluorescence. Results Compared with group S, rats in group C started to show decreases in PWMT on day 3 after operation [(13.46±1.67) g vs(4.65±0.46) g], which was maintained until 12 h after injection (P<0.05). Compared with group S, the number of astrocyte cells in group C[(103±7) vs (402±20)] were significantly increased 2 h after injection (P<0.05). Compared with group C, group G showed remarkable increases in PWMT [(2.73±0.57) g vs (7.31±0.55) g] 0.5 h after injection, which was maintained until 8 h after injection (P<0.05). Compared with group C, the number of astrocyte cells in group G(251±20) were significantly decreased 2 h after injection(P<0.05). Conclusions Subcutaneous injection of gaboxadol relieves the mechanical pain in rats, which may be associated with inhibited activation of astrocytes in the spinal cord. Key words: Neuropathic pain; γaminobutyric acid A receptor; Astrocyte; Spinal cord