Abstract:

Objective To investigate the effects of exogenous brain-derived neurotrophic factor (BDNF) on the activation of astrocytes, and analyse the impact of intrathecal injection of activated astrocytes on pain hyperalgia in normal rats. Methods Primary astrocytes cultured in vitro were incubated with exogenous BDNF (100 ng/mL) for 0 min (baseline), 15 min, 60 min and 120 min, and the expression of glial filament acidic protein (GFAP) in cells was detected by Western blotting. Twenty-four male SD rats were randomly divided into activated-astrocytes group (intrathecal injection of astrocytes incubated with BDNF for 15 min), negative control group (intrathecal injection of astrocytes without incubation with BDNF), placebo group (intrathecal injection of PBS) and blank control group after intrathecal catheterization, with 6 rats in each group. Before injection and 0.5 h, 2 h, 4 h and 8 h after injection, values of 50% mechanical paw withdrawal threshold (50% PWT) were measured with von Frey filaments method. Results The expression of GFAP protein in astrocytes after incubation with BDNF for 15 min, 60 min and 120 min was significantly higher than that of the baseline (P<0.01). In activated-astrocytes group, 50%PWT at each time point after injection was significantly lower than that before injection (P<0.01). In negative control group, transient decrease of 50%PWT only occurred 30 min after injection, which was significantly different from that before injection (P<0.01). There was no significant difference between 50%PWT at each time point after injection and that before injection in placebo group and blank control group (P>0.05). Conclusion Exogenous BDNF can activate astrocytes cultured in vitro, and intrathecal injection of exogenous BDNF-activated astrocytes can directly induce pain hyperalgia in normal rats.

Key words: brain-derived neurotrophic factor, astrocyte, pain hyperalgia