Evaluation of analgesic properties of petroleum ether extract of Zingiber officinale

Background: Herbal remedies and alternative therapies have been employed in the treatment of pain from time immemorial. Ginger is a widely used spice with a lot of medicinal properties, and it is especially soothing to the gastro-intestinal system. Most of the analgesics used in modern medicine have side effects to either gastro-intestinal tract or nervous system. Ginger has neither. Scientific evaluation of the analgesic properties of Zingiber officinale is needed. Aim and Objective: The aim of the study was to evaluate the analgesic effect of three doses of orally administered petroleum ether extract of Z. officinale and to compare with morphine. When tested for analgesic activity, to find out the difference in reaction time at various time intervals for each dose of the extract, and their significance. Materials and Methods: Petroleum ether extract of Z. officinale rhizomes was used. Wistar strain albino rats (150-200 g) and Swiss albino mice (20-25 g) housed under standard laboratory conditions were used. The central analgesic activities of the extract were evaluated by the tail clip method and hot plate method. Statistical analysis was done by one-way analysis of variance to compare the means in the experimental groups. Results: In tail clip method, pain was mechanically induced pain and the pain threshold was measured in terms of mice’ reaction time in seconds. All doses of the extract of Z. officinale were capable of increasing the reaction time in mice during the various time periods. Maximum analgesic activity was shown by 800 mg/kg of the extract at 90 minutes. In hot plate test, maximum analgesic activity was shown by 800 mg/kg of the extract at 180 min. At 30 and 60 min, 800 mg/kg of the extract was as effective as the standard drug, morphine. Conclusions: The study revealed that Z. officinale has significant analgesic properties especially in higher doses.

Pulse-train Stimulation of Primary Somatosensory Cortex Blocks Pain Perception in Tail Clip Test

Human studies of brain stimulation have demonstrated modulatory effects on the perception of pain. However, whether the primary somatosensory cortical activity is associated with antinociceptive responses remains unknown. Therefore, we examined the antinociceptive effects of neuronal activity evoked by optogenetic stimulation of primary somatosensory cortex. Optogenetic transgenic mice were subjected to continuous or pulse-train optogenetic stimulation of the primary somatosensory cortex at frequencies of 15, 30, and 40 Hz, during a tail clip test. Reaction time was measured using a digital high-speed video camera. Pulse-train optogenetic stimulation of primary somatosensory cortex showed a delayed pain response with respect to a tail clip, whereas no significant change in reaction time was observed with continuous stimulation. In response to the pulse-train stimulation, video monitoring and local field potential recording revealed associated paw movement and sensorimotor rhythms, respectively. Our results show that optogenetic stimulation of primary somatosensory cortex at beta and gamma frequencies blocks transmission of pain signals in tail clip test.