Role of BDNF-AS in amygdala in development of neuropathic pain in rats / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the role of brain-derived neurotrophic factor-antisense long-chain non-coding RNA (BDNF-AS) in amygdala in the development of neuropathic pain (NP) in rats.Methods:Healthy clean-grade male Sprague-Dawley rats, aged 2 months, weighing 200-260 g, were used to develop NP model via ligation of left L 5-6 spinal nerve, while control group was only subjected to the exposure of L 5-6 spinal nerve without ligation.This study was performed in two parts.Experiment Ⅰ Fifty-six rats were divided into 3 groups by the random number table method: sham operation group (Sham group, n=8), NP group ( n=24) and BDNF ( n=24). In BDNF group, exogenous BDNF was injected into bilateral amygdala at 1, 3, 6, 13 and 20 days after development of the model, with 100 pmol at each side.Eight rats were sacrificed at 7, 14 and 21 days after the model was developed in NP and BDNF groups and after the model was developed in Sham group, the brains were removed, and the amygdala was isolated for determination of the BDNF content (by enzyme-linked immunosorbent assay), the number of BDNF-positive cells (by immunohistochemistry), and expression of BDNF-AS (by real-time quantitative polymerase chain reaction). Experiment Ⅱ Thirty-two rats were divided into 4 groups ( n=8 each) using the random number table method: Sham operation group, NP group, BDNF group and siRNA group.At 1, 3, 6, 13 and 20 days after development of the model, exogenous BDNF 100 pmol and siRNA-BDNF-AS 50 nmol were injected into the amygdala at each side in BDNF group and siRNA group, respectively.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured before development of the model (T 0) and at 4, 7, 14 and 21 days after development of the model (T 1-4). After the last behavioral test was completed, the rats were sacrificed, and the spinal cord tissues were collected to measure the contents of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α). Results:Experiment Ⅰ Compared with Sham group, the content of BDNF and the number of BDNF positive cells were significantly decreased, and the expression of BDNF-AS was up-regulated at each time point after development of the model in group NP ( P<0.05). Compared with NP group, the content of BDNF and the number of BDNF positive cells were significantly increased, and the expression of BDNF-AS was down-regulated at each time point after development of the model in group NP ( P<0.05). Experiment Ⅱ Compared with Sham group, MWT was significantly decreased and TWL was shortened at T 1-4, and the contents of IL-1β, IL-6 and TNF-α were increased in NP, BDNF and siRNA groups ( P<0.05). Compared with NP group, MWT was significantly increased and TWL was prolonged at T 1-4, and the contents of IL-1β, IL-6 and TNF-α were decreased in BDNF and siRNA groups ( P<0.05). Conclusions:The mechanism underlying the development of NP may be related to the up-regulation of BDNF-AS expression in amygdala, inhibition of BDNF synthesis and promotion of inflammatory responses in the spinal cord of rats.