A direct involvement of the central nervous system in hypophagia and inhibition of respiratory rate in rats after treatment with O,O,S-trimethyl phosphorothioate

Toxicity evaluation of the aqueous extract of the rhizome of Elephantorrhiza elephantina (Burch.) Skeels. (Fabaceae), in rats

Elephantorrhiza elephantina root extract has been used as a traditional remedy for a wide range of ailments both in humans and livestock. As part of the safety assessment of the extract, acute, sub-acute and chronic toxicity tests were conducted by the oral route in rats. Male and female rats were divided into four groups consisting of five rats each and given doses of 200-1600 mg/kg bwt, 200-800 mg/kg bwt and 50-400mg/kg bwt in acute (1 day), sub-acute (14 days) and chronic toxicity (35 days), respectively. During the experiment, no deaths were observed in any groups and there were no remarkable changes in general appearance, as well as in food and water consumption. Significant (P<0.05) changes were however noted in body weights, haematological and serum biochemical parameters between the control and treated groups. Histopathological changes were also noted in kidneys, lungs, liver and spleen of rats receiving high doses. Based on these findings, it can be inferred that the plant has some potential toxicity at certain dose levels; therefore caution has to be taken when using E. elephantina for medicinal purposes.

Roles of neuropeptides in O,O,S-trimethylphosphorothioate (OOS-TMP)-induced anorexia in mice

O,O,S-Trimethylphosphorothioate (OOS-TMP), an impurity present in various organophosphorus insecticides, has previously been shown to induce hypophagia. The major goal of this study was to investigate its mechanism of action. Both intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) injection transiently induced hypophagia at a dose of 5mg/kg within 6h, without causing lung injury. Hypophagia was accompanied by up-regulation of corticotropin releasing factor (CRF) (2.92+/-0.45 vs. 1.7+/-0.5, at 2h after i.c.v., 3.40+/-1.38 vs. 1.76+/-0.41 at 6h after i.p., P<0.05) in the hypothalamus. After i.c.v. injection, hypophagia recovered by 6h after dosing. At doses higher than 5mg/kg, i.c.v. injection induced continuous hypophagia from 20min to 72h after dosing, accompanied by hypothermia and lung injury. OOS-TMP was considered to induce hypophagia through enhancing expression of CRF.