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Objective To evaluate the effect of oxycodone on function of GABAA receptors in dor-sal root ganglion ( DRG ) neurons of rats with neuropathic pain ( NP ) . Methods Thirty-six adult male Sprague-Dawley rats, weighing 180-220 g, aged 10 weeks, were allocated into 3 groups ( n=12 each) u-sing a random number table method: sham operation group ( group S ) , group NP and oxycodone group ( group O) . The sciatic nerve was only isolated but not ligated in group S. NP was induced by chronic con-striction injury. The sciatic nerve was exposed and 4 loose ligatures were placed on the sciatic nerve at 1 mm intervals with 4-0 chromic catgut. Oxycodone 15μg∕kg was intraperitoneally injected once a day for 14 con-secutive days from ligating the sciatic nerve to satisfaction in group O. The thermal paw withdrawal latency( TWL) was measured at 1 day before establishing the model ( T0 ) and 3, 5, 7, 10 and 14 days after es-tablishing the model ( T1-5 ) . The rats were sacrificed after measurement of pain threshold at T5 , and DRG neurons were acutely isolated for recording the amplitude of GABAA receptors-activated currents using whole-cell patch-clamp technique. Results Compared with group S, the TWL was significantly shortened at T1-5, and the amplitude of GABAA receptors-activated currents in DRG neurons was decreased in NP and O groups (P<0. 05). Compared with group NP, the TWL was significantly prolonged at T1-5, and the ampli-tude of GABAA receptors-activated currents in DRG neurons was increased in group O ( P<0. 05) . Conclu-sion Oxycodone can enhance the function of GABAA receptors-activated currents in DRG neurons and thus enhance GABAA receptors-mediated presynaptic inhibition, which may be related to the mechanism of oxyc-odone-induced reduction of NP in rats.
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Objective:To observe the effects of 0.4 μg/(kg·h)dose of dexmedetomidine on intra-operative wake-up test in children patients undergoing scoliosis surgery.Methods:Sixty patients for pos-terior scoliosis correction (ASA Ⅰ -Ⅱ,aged 5 -16 years)from March 2013 to April 2015 were en-rolled in this prospective,double-blinded,randomized,placebo-controlled study,The patients were ran-domly classified into two groups to receive dexmedetomidine (group RD,n =30)or saline solution (group R,n =30).In group RD,dexmedetomidine [0.4 μg/(kg·h)]was administered after tracheal intubation,while the equal volume saline solution was given instead in group R.Anesthesia was induced with midazolam,propofol,sufentanyl and cisatracurium,and anesthesia was maintained with sevoflurane inhalation and a continuous intravenous infusion of remifentanil in the both groups.BIS(bispectral index, BIS)value was maintained at 40 -60,and mean arterial pressure (MAP)was maintained at ≥ 60 mm-Hg before the wake-up test.When the wake-up test was performed,immediately the dexmedetomidine and remifentanil infusion were stopped,and the end-tidal concentration of sevoflurane was adjusted to 0. Mean arterial pressure,and heart rate (HR)were recorded before anesthesia and at 5-minute intervals during the wake-up test.The wake-up test time,arousal quality and sedation scores were recorded also. In addition,the data were also gathered on the dosage of ephedrine and atropine were used,as well as the intraoperative awareness in the patients who were followed up on the first day after the operation.Re-sults:There were no differences between group RD and group R with regard to HR and MAP at getting into the operation room (t =-1.460,P =0.150; t =-1.015,P =0.315 ).In group RD,no evi-dence was found for a difference in HR and MAP at awakening up versus at getting into the operation room (t =0.974,P =0.340;t =-1.449,P =0.161),while in group R,an increase in HR and MAP occurred at awakening versus at getting into the operation room (t =-2.106,P =0.044;t =-2.352, P =0.026).There were no significant differences in sedation scores and wake-up test time between the two groups(t =1.986,P =0.052;t =0.392,P =0.697).The wake-up test quality was significantly bet-ter in group RD than in group R (t =-2.098,P =0.041).HR in group RD was significantly lower than that in group R at any time point during the wake-up test (P <0.05).Four patients had awareness oc-currence during the operation in group R,and no awareness occurrence in group RD.Conclusion:Dexmedetomidine,when administered at a rate of 0.4 μg/(kg·h)as an adjuvant of sevoflurane inhala-tional anesthesia,could improve the wake-up test quality,and maintain hemodynamic stability during scoliosis surgery.
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Objective To evaluate the role of spinal cord CABAA receptors in the analgesic effect of propofol on visceral pain in rats. Methods Adult female SD rats, weighing 190-240 g, were used in this study.The animals were anesthetized with intraperitoneal ketamine 50-100 mg/kg. Intrathecal (IT) catheters were placed at L5-6 interspace according to the technique described by Storkson et al. Thirty-two animals in which IT catheters were successfully placed were randomly divided into 4 groups ( n = 8 each) : dimethyl sulphoxide (DMSO) group (group D), propofol group (group P), bicuculline group (group B) and bicuculline + propofol group (group B +P). Visceral pain was induced by injecting 10% formalin 100 μl underneath the mucous membrane of rectum.Groups D, P and B received IT DMSO 5 μl, propofol 10 μg and bicuculline 2 μg respectively. Group BP received IT bicuculline 2 μg and then IT propofol 10 μg 10 min later. The L5-S1 segment of the spinal cord was removed 2 h after formalin injection to determine FOS protein expression by hnmuno-histochemistry. Results Compared with groups D and B, FOS protein expression was significantly down-regulated in group P ( P ＜ 0.05 ) . There was no significant difference in FOS protein expression between groups D and B ( P ＞ 0.05) . FOS protein expression was significantly up-regulated in group BP compared with group P ( P ＜ 0.05) . Conclusion Propofol has analgesic effect on visceral pain in rats through spinal cord GABAA receptor action.
