Antinociceptive activity of the chloroform fraction of Dioclea virgata (Rich.) Amshoff (Fabaceae) in mice

Subchronic administration of Parastar insecticide induced behavioral changes and impaired motor coordination in male Wistar rats

Parastar is an insecticide formulation of lambda-cyhalothrin and imidacloprid largely used for crop protection in North West Region of Cameroon. In the present study, we evaluated the behavioral activities and motor function of Wistar male rats after subchronic treatment with the pesticide formulation. To this end, three groups of adult rats were administered Parastar at doses 1.25, 2.49 and 6.23 mg/kg, respectively, for 35 days. A control group was included and received distilled water. At the end of the treatment, the animals were submitted to behavioral and functional tests (open field test, elevated plus maze test, light-dark box test, forced swimming test, tail suspension test, beam-walking test, grid suspension test and wire hang test) for estimation of anxiety, exploration, depression and motor coordination. Results revealed that Parastar, at the higher doses tested, 2.49 and 6.23 mg/kg, induced anxiogenic-like pattern behavior in rats in all behavioral assays including open field test (total distance moved, total lines crossed, frequency and total time in center square were all reduced), elevated plus maze (decreased total time spent in open arms and the number of entries in open arms of the elevated plus maze), and light-dark box (the dark box duration increased, while light box duration time and frequency of transition between dark and light box decreased). Treatment with 2.49 and 6.23 mg/kg Parastar increased the immobility time of animals in both forced swimming test and tail suspension test. The insecticide induced decrease in the distance traveled, foot slip and number of turns of animals in the beam walking test. Parastar also decreased the animal suspension time in both grid suspension grip-strength test and the wire hang test. Taken altogether, these results suggest that subchronic administration of Parastar at the doses of 2.49 and 6.23 mg/kg induced anxiety-like and depressive-like behavior as well as impaired motor coordination and muscle strength in male rats.

Effects of silymarin on neuropathic pain and formalin-induced nociception in mice

OBJECTIVES

Based on the previous reports, silymarin can suppress nitric oxide, prostaglandin E2 (PGE2), leukotrienes, cytokines production, and neutrophils infiltration. Regarding the fact that inflammation plays an important role in neuropathic and formalin-induced pain, it was assumed that silymarin could reduce pain. The present study investigates the analgesic effects of silymarin in chemical nociception and a model of neuropathic pain.

MATERIALS AND METHODS

Chemical nociception was produced by injection of 20 µl of formalin (0.5% formaldehyde in saline) into the plantar region of the right hind paw. A sciatic-nerve ligated mouse was applied as the model of neuropathic pain and the antinociceptive response of silymarin was examined 14 days after unilateral nerve-ligation using the hot plate test.

RESULTS

The intraperitoneal administration of silymarin (25, 50, and, 100 mg/kg) 2 hr prior to the intraplantar formalin injection suppressed the nociceptive response during the late phase of the formalin test significantly, but it was not in a dose-dependent manner. Different doses of silymarin 14 days after unilateral sciatic nerve ligation in hot plate test did not induce obvious antinociception.

CONCLUSION

Results of the present study indicated that repeated administration of silymarin prevents the formalin-induced nociceptive behavior. However, it is not effective in the treatment of sciatic neuropathic pain.

Pharmacological evaluation of sedative-hypnotic activity and gastro-intestinal toxicity of Rhizoma Paridis saponins

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizoma Paridis saponins (RPS) have been well studied for antimicrobial, anti-hemorrhagic, and anticancer effects. However, scientific information on RPS regarding the toxic and neuropharmacological effects is limited. In this study, the acute oral toxicity, sedative-hypnotic activity and gastro-intestinal toxicity of RPS were investigated.

MATERIALS AND METHODS

The acute toxicity was carried out by administering single doses (800-5000 mg/kg) of RPS to adult mice. Rotarod test and sodium pentobarbital-induced hypnosis activity were used to evaluate the neuropharmacological effects on mice. Gastric emptying and intestinal transit were used to investigate the gastric-intestinal system effects.

RESULTS

A single oral administration of RPS dose-dependently caused adverse effects on the general behavior and mortality rate of mice. LD(50) value of oral acute toxicity was 2182.4 mg/kg, with 95% confidence limit of 1718.4-2807.8 mg/kg. In the test of sleeping mice, RPS acted in synergy with sodium pentobarbital at doses 250 and 500 mg/kg while motor coordination was not influenced within 120 min after treatment with RPS. Regarding the gastric-intestinal toxicity, RPS (100, 250, and 500 mg/kg) significantly inhibited gastric emptying but did not affect the intestinal transit.

CONCLUSIONS

RPS, which is a hypotoxic anticancer drug, possesses the sedative-hypnotic activity and gastric stimulus side effect.