Korean J Pain.  2007 Dec;20(2):106-110. 10.3344/kjp.2007.20.2.106.

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

• Kim WM
• Yoon MH
• Lee HG
• Han YG
• Kim YO
• Huang LJ
• Cui JH

• KMID: 2278049
• DOI: http://doi.org/10.3344/kjp.2007.20.2.106

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.

Keyword

antinociception; formalin test; GABA receptors; intrathecal; rat; sildenafil

MeSH Terms

Acute Pain
Animals
Bicuculline
Catheterization
Catheters
Cyclic Nucleotide Phosphodiesterases, Type 5
Formaldehyde*
GABA Antagonists
Humans
Injections, Subcutaneous
Male
Nociception
Pain Measurement*
Rats*
Receptors, GABA
Sildenafil Citrate
Bicuculline
Cyclic Nucleotide Phosphodiesterases, Type 5
Formaldehyde
GABA Antagonists
Receptors, GABA