The influence of GABA-ergic system on clonidine analgesia in rats

The effect of agonists and antagonists of GABA-ergic system on analgesia induced by clonidine was investigated in the rat. The compounds activating (muscimol, 1 mg/kg and aminooxyacetic acid; AOAA, 25 mg/kg) or inhibiting GABA-ergic receptors (bicuculline and picrotoxin, in subconvulsive doses 0.5-1 mg/kg) do not change clonidine-induced analgesia. Only the higher dose (2 mg/kg) of muscimol, bicuculline or picrotoxin affected clonidine-induced analgesia. Baclofen, contrary to other GABA agonists, markedly potentiated clonidine-induced analgesia in the dose dependent manner. These results suggest that compounds activating and inhibiting GABA A receptors (muscimol, AOAA, bicuculline and picrotoxin) have a weak influence on clonidine induced analgesia as compared to the effect of baclofen (agonist of GABA B receptors).