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. 2014 Fall;2(4):151-7.

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

Marjan Hosseini  1 , Zohreh Karami  1 , Atousa Janzadenh  2 , Seyed Behnamedin Jameie  3 , Zahra Haji Mashhadi  1 , Mahmoud Yousefifard  1 , Farinaz Nasirinezhad  4
Affiliations

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

Marjan Hosseini et al. Emerg (Tehran). 2014 Fall.

Abstract

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 introduced for pain management. Thus, the present study was performed to evaluate the pain alleviating effect of intrathecal injection of different doses of muscimol as GABAA receptor agonist in spinal cord injury (SCI) model of neuropathic 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. Neuropathic pain symptoms were assessed at before treatment, 15 minutes, one hour and three hours after muscimol administration. 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 improve 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 did not 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 present study revealed that using muscimol with doses of 0.01µg, 0.1µg, and 1 µg reduces the symptoms of neuropathic pain. In addition, the effect of GABAA agonist is short term and its effectiveness gradually decreases by time.

Keywords: GABAA receptor agonists; Neuropathic pain; muscimol; pain management.

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Figures

Figure 1
Figure 1
Effectiveness of different muscimol dose administration on reducing the neuropatic pain. Data eas peresent as Mean±SEM A: heat hyperallgesia; B: mechanical hyperallgesia; C: cold allodynia; D: mechanical allodynia. **have a significant difference in p<0.001 with before administration time; *shows a significant difference in p<0.01 with before administration time. The significance level was defined in terms of Two-way ANOVA test.
Figure 2
Figure 2
Effectiveness of various muscimol doses on reducing the neuropatic pain symptoms in corresponding times. A: heat hyperallgesia; B: mechanical hyperallgesia; C: cold allodynia; D: mechanical allodynia. The significance level was evaluated based on ANCOVA test. No significant difference was seen among various doses in evaluated times to reduce the neuropathic pain symp-toms
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