Role of monocyte chemoattractant factor∕chemokine C-C receptor 2 pathway in amygdala in neuro-pathic pain in rats / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the role of monocyte chemotactic factor-1 (MCP-1)∕chemokine C-C receptor 2 ( CCR2) in amygdala in neuropathic pain ( NP) in rats. Methods Clean-grade healthy male Sprague-Dawley rats, weighing 200-260 g, aged 2 months, in which NP model was established by ligating the left L5,6spinal nerve, were used in this study. The experiment was performed in two parts. Ex-periment Ⅰ Thirty-two rats were divided into 2 groups using a random number table method: control group (C group, n＝8) and NP group (n＝24). Rats were sacrificed at 7, 14 and 21 days after establis-hing NP model in group NP or at the corresponding time points before establishing NP model in group C, and the amygdala was removed for determination of the expression of MCP-1 and CCR2 mRNA and positive cell count using quantitative real-time polymerase chain reaction and immunohistochemistry. Experiment ⅡThirty-two rats were divided into 4 groups ( n＝8 each) using a random number table method: control group (C group), NP group, MCP-1 group and specific CCR2 antagonist RS102895 group (RS group). MCP-1 (50 pmol for each side) or RS102895 (100 pmol for each side) was injected into the bilateral a-mygdala at days 3, 6, 13 and 20 after establishing NP model in MCP-1 and RS groups, respectively. The thermal paw withdrawal latency (TWL) and mechanical paw withdrawal threshold (MWT) were measured at days 4, 7, 14 and 21 after establishing NP model (T1-4). Rats were sacrificed at T4and the L5segment of the spinal cord was removed for determination of interleukin-1beta (IL-1β), IL-6 and tumor necrosis fac-tor-alpha ( TNF-α) contents by enzyme-linked immunosorbent assay. Results Experiment Ⅰ Compared with group C, the expression of MCP-1 and CCR2 mRNA in amygdala was significantly up-regulated, and the number of MCP-1 and CCR2 positive cells was increased in group NP ( P＜0. 05). Experiment ⅡCompared with group C, the MWT was significantly decreased and TWL was shortened at T1-4, and the contents of IL-1β, IL-6 and TNF-α were increased in the other three groups ( P＜0. 05). Compared with group NP, the MWT was significantly decreased and TWL was shortened at T1, and the contents of IL-1β, IL-6 and TNF-α were increased in group MCP-1, and the MWT was significantly increased and TWL was prolonged at T1-4, and the contents of IL-1β, IL-6 and TNF-α were decreased in group RS ( P＜0. 05 or 0. 01). Conclusion Enhanced function of MCP-1∕CCR2 in amygdala may be involved in the pathophysio-logical process of NP in rats.