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Abstract
Background and Aims Hypertonic saline is used for treating chronic pain, but clinical studies with optimal therapy protocols are lacking. This study aimed to determine the concentration at which the effect reaches its peak and the antinociceptive mechanism of Hypertonic saline.
Flowchart of the GABA antagonist experiment
Methods A spinal nerve ligation (SNL, left L5, and L6) model was used to induce neuropathic pain in rats weighing 250–300 g. One week after implantation of the intrathecal catheter, different concentrations of NaCl were injected intrathecally into the rats. Behavioral tests (von Frey filaments, hot-plate, and cold-plate tests) were used to derive the results at baseline, 30 minutes, 2 hour, 1 day, and 1 week. After the same preparation, the rats were randomly divided into four groups of 10: the control group, hypertonic group, bicuculline group, and phaclofen group. Behavioral tests were then performed at weeks 1 and 3 after each drug administration, which followed the administration of intrathecal 5% NaCl. This study was reviewed and apporoved by the Institutional Animal Care and Use Committee Asan Institute for Life Sciences.
Results Using more than 5% NaCl in the rats induced mechanical allodynia and thermal hyperalgesia has a significant therapeutic effect. Moreover, more than 5% NaCl showed a partial time- and dose-dependent antinociceptive effect on cold hyperalgesia. Pretreatment of the γ-Aminobutyric Acid (GABA) receptor antagonist inhibited the antinociceptive effect of hypertonic saline in the SNL rats.
Conclusions Intrathecally injected hypertonic saline is effective at concentrations greater than 5% for treating neuropathic pain, and its effects may be associated with the GABAA and GABAB receptors.