Intracisternal or intrathecal glycine, taurine, or muscimol inhibit bicuculline-induced allodynia and thermal hyperalgesia in mice

Aim: To investigate the effects of GABA and glycine on analgesia in the central nervous system.Methods:Glycine, taurine, or muscimol was injected with bicuculline into the cistern magna or the lumbar subarachnoidal space in ICR mice. The effects on bicuculline-induced allodynia in a touch-evoked agitation test and on pain threshold index in a hot-plate test were assessed. Results: The dosages of the amino acids administered with bicuculline had no effect on motor behavior in conscious mice. Glycine or muscimol reduced bicuculline-induced allodynia regardless of the administration site, whereas intrathecal taurine reduced bicuculline-induced allodynia. Glycine, taurine, and muscimol all antagonized the effects induced by bicuculline in the hot-plate test, regardless of the administration site. Conclusion: Glycine, taurine, and muscimol were found to have anti-allodynic and anti-thermal hyperalgesic properties in vivo. These observations suggest an interaction between glycine and GABA receptors during the regulation of antinociception.