J Korean Med Sci.  2013 Aug;28(8):1238-1243. 10.3346/jkms.2013.28.8.1238.

Antinociceptive Effects of Amiloride and Benzamil in Neuropathic Pain Model Rats

• Jeong S
• Lee SH
• Kim YO
• Yoon MH

• KMID: 1793032
• DOI: http://doi.org/10.3346/jkms.2013.28.8.1238

Abstract

Amiloride and benzamil showed antinocicepitve effects in several pain models through the inhibition of acid sensing ion channels (ASICs). However, their role in neuropathic pain has not been investigated. In this study, we investigated the effect of the intrathecal amiloride and benzamil in neuropathic pain model, and also examined the role of ASICs on modulation of neuropathic pain. Neuropathic pain was induced by L4-5 spinal nerve ligation in male Sprague-Dawley rats weighing 100-120 g, and intrathecal catheterization was performed for drug administration. The effects of amiloride and benzamil were measured by the paw-withdrawal threshold to a mechanical stimulus using the up and down method. The expression of ASICs in the spinal cord dorsal horn was also analyzed by RT-PCR. Intrathecal amiloride and benzamil significantly increased the paw withdrawal threshold in spinal nerve-ligated rats (87%+/-12% and 76%+/-14%, P=0.007 and 0.012 vs vehicle, respectively). Spinal nerve ligation increased the expression of ASIC3 in the spinal cord dorsal horn (P=0.01), and this increase was inhibited by both amiloride and benzamil (P<0.001 in both). In conclusion, intrathecal amiloride and benzamil display antinociceptive effects in the rat spinal nerve ligation model suggesting they may present an alternative pharmacological tool in the management of neuropathic pain at the spinal level.

Keyword

Amiloride; Benzamil; Acid Sensing Ion Channels; Spinal Nerve Ligation; Spinal Cord Dorsal Horn

MeSH Terms

Acid Sensing Ion Channels/genetics/metabolism
Amiloride/*analogs & derivatives/pharmacology/*therapeutic use
Analgesics/pharmacology/*therapeutic use
Animals
Disease Models, Animal
Male
Neuralgia/*drug therapy
RNA, Messenger/metabolism
Rats
Rats, Sprague-Dawley
Reverse Transcriptase Polymerase Chain Reaction
Spinal Cord/metabolism
Transcription, Genetic/drug effects
Acid Sensing Ion Channels
Amiloride
Analgesics
RNA, Messenger

Figure

• 

  Fig. 1 Effects of intrathecal amiloride on the hindpaw withdrawal response after spinal nerve ligation. Data are presented as the withdrawal threshold (g) or the percentage of the maximal possible effect (%MPE). Each line or bar represents the means±SEM of 5-7 rats. Baseline data (BL) were measured immediately before intrathecal delivery of drugs or vehicle. Intrathecal amiloride produced an increase of the withdrawal threshold. *P<0.05 vs vehicle group as determined by one-way analysis of variance with Scheffe's post hoc test.

• 

  Fig. 2 Effects of intrathecal benzamil on the hindpaw withdrawal response after spinal nerve ligation. Data are presented as the withdrawal threshold (g) or the percentage of the maximal possible effect (%MPE). Each line or bar represents the means±SEM of 5-7 rats. Baseline data (BL) were measured immediately before intrathecal delivery of drugs or vehicle. Intrathecal benzamil produced an increase of the withdrawal threshold. *P<0.05 vs vehicle group as determined by one-way analysis of variance with Scheffe's post hoc test.

• 

  Fig. 3 Acid-sensing ion channel (ASIC) expression in the rat spinal dorsal horn (n=5, each group). Data are presented as the means±SEM. All subtypes of ASIC except ASIC2 are expressed in the rat spinal dorsal horn. The expression of ASIC3 was increased in the spinal dorsal horn following spinal cord ligation. *P<0.01 vs naive group as determined by one-way analysis of variance with Scheffe's post hoc test. SNL, spinal nerve-ligated group.

• 

  Fig. 4 Effects of Amiloride and benzamil on ASIC3 expression in the rat spinal dorsal horn. Data are presented as the means±SEM. Amiloride and benzamil significantly inhibited the increase in ASIC3 expression after spinal cord ligation. *P<0.001 vs spinal nerve-ligated group as determined by one-way analysis of variance with Scheffe's post hoc test. SNL, spinal nerve-ligated group.

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