Effect of electric stimulation of vagus nerves on expression of aquaporin-4 in brain tissues of rats with endotoxemia

Abstract

Objective To evaluate the effect of electric stimulation of vagus nerves on the expression of aquaporin-4 (AQP-4) in brain tissues of rats with endotoxemia. Methods Forty-eight adult male Sprague-Dawley rats, aged 2 months, weighing 200-250 g, were divided into 4 groups (n=12 each) using a random number table: sham operation group (S group), endotoxemia group (E group), vagus nerve transection group (VNT group) and vagus nerve transection plus vagus nerve stimulation group (VNT+ VNS group). The model of endoxemia was established by injection of lipopolysaccharide 10 mg/kg via the femoral vein of anesthetized rats.Left cervical vagotomy was performed at 30 min before injection of lipopolysaccharide in VNT and VNT+ VNS groups.In VNT+ VNS group, electric stimulation of the distal end of the left vagus nerve was performed immediately after the end of surgery.Stimulation parameters were as follows: current intensity 0.5 mA, pulse width 0.5 ms, frequency 20 Hz, once every 5 min, 30 s per time, lasting for 1 h. Blood samples were collected from the abdominal aorta at 6 h after establishment of the model, and then the rats were sacrificed and brains were removed.The level of IL-1β in plasma and brain tissues and content of AQP-4 in brain tissues were measured by enzyme-linked immunosorbent assay.The Evans blue (EB) content in brain tissues and brain water content were determined. Results Compared with S group, the levels of IL-1β in plasma were significantly increased, and the contents of IL-1β, AQP-4 and EB in brain tissues and brain water content were increased in E, VNT and VNT+ VNS groups (P 0.05). Conclusion The mechanism by which electric stimulation of vagus nerves reduces brain injury may be related to decreased content of AQP-4 in brain tissues of rats with endotoxemia. Key words: Vagus nerve; Electric stimulation therapy; Endotoxemia; Brain; Aquaporin 4