Effect of pulsed radiofrequency on phenotypic transformation of lumbar sympathetic ganglion in rats with diabetic neuropathic pain

Abstract

Objective To evaluate the effect of pulsed radiofrequency (PRF) on the phenotypic transformation of the lumbar sympathetic ganglion (LSG) in the rats with diabetic neuropathic pain (PDN). Methods Twenty-four clean-grade healthy adult male Sprague-Dawley rats, aged 2 months, weighing 180-220 g, were divided into 4 groups (n=6 each) according to the method of random number table: control group (group C), group PDN, group PRF, and PRF control group (group PC). The PDN model was established by intraperitoneal injection of streptozotocin 60 mg/kg in anesthetized rats.Citrate-sodium citrate buffer 6 ml/kg was intraperitoneally injected in group C. Group PC only received radiofrequency needle puncture.PRF was performed on the right L3 LSG in group PRF.The mechanical paw withdrawal threshold (MWT) to von Frey filament stimulation was measured before intraperitoneal injection (baseline, T0), before PRF and at 1, 3, 5, 7 and 14 days after PRF.The rats were then sacrificed, and ipsilateral L3 LSGs were removed for determination of the expression of tyrosine hydroxylase (TH) and vesicle glutamate transporter2 (VGLUT2) in LSGs (by double immunofluorescent staining) and for examination of pathological changes (with a light microscope). The number of neurons expressing VGLUT2 was counted. Results Compared with group C, the MWT was significantly decreased at T1-6, and the number of neurons expressing VGLUT2 was increased at T6 in PDN, PC and PRF groups (P<0.05). Compared with PDN and PC groups, the MWT was significantly increased at T2-6, and the number of neurons expressing VGLUT2 was decreased at T6 in group PRF (P<0.05). TH expression in LSGs was found, and no VGLUT2 expression in LSGs was observed in group C, the expression of TH and VGLUT2 in LSGs was found in the other three groups, especially in PDN and PC groups, and most of the neurons expressing VGLUT2 expressed TH simultaneously. Conclusion The mechanism by which PRF mitigates PDN is related to inhibiting the phenotypic transformation of LSGs in the rats. Key words: Pulsed radiofrequency treatment; Diabetes mellitus; Neuralgia; Ganglia, sympathetic; Phenotype