[Role of gonadectomy in development of hyperalgesia induced by partial sciatic nerve ligation in male mice]

ABSTRACT

Neuropathic pain arising from sciatic nerve ligation [SNL] injury can result in increased sensitivity to both noxious [hyperalgesia] and non-noxious stimuli [allodynia]. Some research studies have been shown that the mechanisms underlying neuropathic pain processing differed as a function of gender and gonadal hormone status. In this study, we try to show the effects of nerve injury after gonadectomy in time-course of hyperalgesia that has not been extensively studied. 45 albino male mice weighting 25-35 gr were subjected to Intact, Shamoperated, Sciatic Nerve Ligated, Gonadectomized, and Sciatic Nerve Ligated+Gonadectomized groups. The tail flick latency was measured at set intervals 10[th]-20[th] days for 11 days after surgical operation [peripheral nerve injury by left sciatic nerve ligation and gonadectomy] in all groups by tail flick analgesiometer. The gonadectomized mice responded [7.15 +/- 1.8 sec] significantly faster than intact ones [10.78 +/- 1.43 sec] to a thermal nociceptive stimulus [Pmice, hyperalgesia developed significantly within 11-17 days after sciatic nerve ligation [6.35 +/- 1.33 sec; P<0.05]. In sciatic nerve ligated+gonadectomized group, tail flick latency time [5.45 +/- 1.14 sec] decreased significantly within 11 and 13-16 days after surgical operations in comparison with sham-operated mice [9.99 +/- 1.64 sec; P<0.05] and as compared with tail flick latency in sciatic nerve ligated mice [6.62 +/- 1.75 sec] within 13th-14th [P<0.05] and 15[th] [P<0.01] days after surgical operations. It was concluded that testosterone might play a role in the pain modulation. In addition, we suggest that testosterone also affects neuropathic pain that is accompanied by a number of neuroplastic alternations at the level of spinal cord including up- and down-regulation of neurotransmitters during sciatic nerve ligation-induced hyperalgesia