Objective    To investigate influence of amitriptyline on astrocytic activation in spinal cord of rats after spared nerve injury (SNI).     Methods    A total of 120 male SD rats were randomly divided into 4 groups with 30 rats in each group: control (A)

SNI (B)

amitriptyline (C)

and SNI+amitriptyline (D) groups

which respectively were treated with intraperitoneal injections of 0.2 ml normal saline (A and B)

10 mg/kg amitriptyline (C and D)

bid. The L

3

to L

6

segment of the s

pinal cord was isolated respectively at 1

3 and 5 d after surgery. Expression of glial fibrillary acidic protein (GFAP)

marker of astrocytes

was determined by immunofluorescence

Western blot assay and semiquantitative RT-PCR. The changes of mechanical pain threshold were measured.     Results    Compared with control

group B had a markedly decreased rat mechanical pain threshold (P0.05) and an obviously high expression of GFAP at both protein (0.38±0.24

0.84±0.31 and 1.36±0.43) and mRNA (0.55±0.14

0.86±0.16

1.32±0.32) levels at the corresponding time points. However

there was no significant change on these indexes between groups A and C. Mechanical pain threshold of rats in group D did not change any more in 3 and 5 d after surgery (4.5±1.5 and 4.9±1.4 g). In addition

the expression of GFAP at both protein (0.79±0.25

0.77±0.23) and mRNA (0.63±0.06

0.64±0.17) levels in group D were higher than those in control but still lower than those of group B (P0.05) in 3 and 5 d after surgery.     Conclusion    Amitriptyline inhibits the activation of astrocytes in SNI animals

which maybe one of its mechanisms in the treatment of neuropathic pain.