Interactive effect of aqueous-alcoholic extract of ginger as well as GABAA receptor agonist and antagonist on pain sensitivity in male rats

Ginger has shown anti-nociceptive effects. Here we investigated the possible involvement of GABAA receptors in anti-nociceptive effect of ginger using muscimol (GABAA agonist) and picrotoxin (GABAA antagonist) in rats that received ginger. The pain sensitivity was evaluated by formalin test. Thirty-five male Sprague-Dawley rats were randomly divided into 7 groups (n=5): sham1 (received distilled water. PO); sham2 (received water + 0.75μl artificial cerebrospinal fluid by intracerebroventricular (ICV) injection; experimental1 (received ginger at 50 mg/kg/day, PO); experimental2 and 3 (received ginger+ 0.75μl of 250 or 500ng/rat muscimol by ICV injection); experimental4 and 5 (received ginger+ 0.75μl of 250 and 500ng/rat picrotoxin by ICV injection). On day 16 and 30min after ICV injections, formalin test was performed on all rats. Ginger significantly reduced pain sensitivity in both phases of formalin test in comparison to sham1 and 2. In early and late phase, both doses of muscimol reduced pain sensitivity as compared to the ginger group. Picrotoxin at 250ng/rat+ ginger reduced pain sensitivity as compared to the group that received ginger, in both the early and the late phases of the formalin test. Picrotoxin at 500ng/rat+ ginger increased pain sensitivity in the early phase and late phase of formalin test as compared to the ginger group. Aqueous- alcoholic extract of ginger has significant analgesic effects in late phase of formalin test and GABAA receptors may be involved in this regard.