GABAB Receptor Modulation on the Antinociception of Intrathecal Sildenafil in the Rat Formalin Test / 대한통증학회지

ABSTRACT

BACKGROUND: A phosphodiesterase 5 inhibitor, sildenafil, has been effective against nociception. Several lines of evidence have demonstrated the role of the GABAergic pathway in the modulation of nociception. The impact of the GABA receptors on sildenafil was studied using the formalin test at the spinal level. METHODS: Male SD rats were prepared for intrathecal catheterization. The formalin test was induced by subcutaneous injection of formalin solution. The change in the activity of sildenafil was examined after pretreatment with GABA receptor antagonists (GABAA receptor antagonist, bicuculline; GABAB receptor antagonist, saclofen). RESULTS: Intrathecal sildenafil dose-dependently attenuated the flinching observed during phase 1 and 2 in the formalin test. The antinociceptive effect of sildenafil was reversed by the GABAB receptor antagonist (saclofen) but not by the GABAA receptor antagonist (bicuculline) in both phases. CONCLUSIONS: Intrathecal sildenafil suppressed acute pain and the facilitated pain state. The antinociception of sildenafil is mediated via the GABAB receptor, but not the GABAA receptor, at the spinal level.