Effect of oxycodone on function of GABAA receptors in dorsal root ganglion neurons of rats with neuropathic pain / 中华麻醉学杂志

ABSTRACT

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.