The Effect of Intrathecal Administration of Muscimol on Modulation of Neuropathic Pain Symptoms Resulting from Spinal Cord Injury; an Experimental Study

Introduction: Neuropathic pain can be very difficult to treat and it is one of the important medical challenging about pain treatments. Muscimol as a new agonist of gamma-Aminobutyric acid receptor type A (GABAA) have been intro-duced for pain management. Thus, the present study was performed to evaluate the pain alleviating effect of intrathe-cal injection of different doses of muscimol as GABAA receptor agonist in spinal cord injury (SCI) model of neuro-pathic pain. Methods: In the present experimental study male Wistar rats were treated by muscimol 0.01, 0.1 or 1 µg/10ul, intrathecally (i.t.) three weeks after induction of spinal cord injury using compression injury model. Neuro-pathic pain symptoms were assessed at before treatment, 15 minutes, one hour and three hours after muscimol ad-ministration. The time of peak effect and optimum dosage was assessed by repeated measures analysis of variance and analysis of covariance, respectively. Results: Muscimol with the dose of 0.01 µg in 15 minutes caused to im-prove the thermal hyperalgesia (df: 24, 5; F= 6.6; p < 0.001), mechanical hyperalgesia (df: 24, 5; F= 7.8; p < 0.001), cold allodynia (df: 24, 5; F= 6.96; p < 0.001), and mechanical allodynia (df: 24, 5; F= 15.7; p < 0.001). The effect of doses of 0.1 µg and 1 µg were also significant. In addition, the efficacy of different doses of muscimol didnʹt have difference on thermal hyperalgesia (df: 24, 5; F= 1.52; p= 0.24), mechanical hyperalgesia (df: 24, 5; F= 0.3; p= -0.75), cold allodynia (df: 24, 5; F= 0.8; p= -0.56), and mechanical allodynia (df: 24, 5; F= 1.75; p= 0.86). Conclusion: The finding of the pre-sent study revealed that using muscimol with doses of 0.01µg, 0.1µg, and 1 µg reduces the symptoms of neuropathic pain. Also the effect of GABAA agonist is short term and its effectiveness gradually decreases by time.