Antinociceptive Effect of Aqueous Extract of Origanum vulgare L. in Male Rats: Possible Involvement of the GABAergic System

The objective of the present investigation was to assess the possible involvement of GABAergic mechanism in analgesic effect of aqueous extract of Origanum Vulgare (ORG) in a rat model of acute pain test. Sixty-three anaesthetized male Wistar rats (200-250 g) were cannulated into the left ventricle. Five to seven days after the recovery from surgery, ORG extract was intraventricularly injected at dose of 3 μg/rat i.c.v. Then, baclofen (10 mg/Kg, IP), CGP35348 (100 nmol/Kg, i.c.v), muscimol (1 mg/Kg IP) and bicuculline (5 mg/Kg IP) were separately injected 20 min before the injection of ORG. The experimental groups were compared with intact (control) group (n = 7). The response latency of rats to thermal stimulation was recorded using Tail-Flick test. Injection of ORG extract resulted in a significant and dose-dependent increase in the response latency. There was also a significant increase in the response latency after co-administration of ORG extract with baclofen when compared with control group. However, following co-administration of ORG extract/bicuculline, a significant decrease in the response latency was observed compared to control group. In conclusion, the results of the present study suggest that aqueous extract of Origanum vulgare L. ssp. viridis possesses antinociceptive activity in a dose-dependent manner and ORG-induced antinociception might be mediated, at least in part, by both GABA receptors.