Dynamic Changes of Neurotrophin-3 Expression in Brain Injury After Antibiotic Therapy of Meningitis Induced by Streptococcus Pneumoniae

Abstract

Objective To investigate the expression of neurotrophin-3 (NT-3) expression in brain injury after antibiotic therapy of meningitis induced by Streptococcus pneumoniae. Methods A total of 46 SD rats, 3-week old, either male or female, received 10% chloral hydrate at the concentration (0.15-0.30)mL/100 g by intraperitoneal injection. Among them, 34 rats were established the brain damage in pneumococcal meningitis model successfully, which were divided into infection group (n=20) and treatment group (n=14). The rest rats were included into control group(n=12). There was no significant difference of average weight and age among three group (P>0.05). ①All of them underwent cisternal puncture. Infection group and treatment group received an equivalent volume of a Streptococcus pneumoniae suspension and control group received sterile saline as a placebo. The expression of neurotrophin-3 in the brain were observed (×400). The rats were sacrificed at 24 h or 5 d post-infection and cortex were harvested (24 h infection group and 5 d infection group). The expressions of neurotrophin-3 protein were detected by immunohistochemical staining methods in cerebral cortex and hippocampus. ② Infection group were further divided into two sub-groups. Antibiotic treatment group (n=8) received subcutaneous injection of ceftriaxone treatment for 3 days, and antibiotic control group (n=6) received no treatment. ③ Control group were sacrificed immediately after 24 hours, 5 days after receiving saline (24 h control group and 5 d control group). Results In cerebral cortex and hippocampus, the expression of neurotrophin-3 was declined obviously at 24 h infection group and then restored in 5 d infection group, compared to control group (P<0.01, P<0.05). The expression of neurotrophin-3 protein in antibiotic treatment group was lower than that of antibiotic control group (P<0.05). Conclusion The expression of neurotrophin-3 declined in the brain of rats after meningitis induced by Streptococcus pneumoniae. Neurotrophin-3 supporting role in the protection of the nerve may be reduced in Streptococcus pneumoniae meningitis acute brain injury. After administration with antibiotics, neurotrophin-3 expression still at low level and its endogenous neuroprotection may still not be restored. Key words: meningitis; Streptococcus pneumoniae; neurotrophin-3 (NT-3); antibiotics; rat