Effect of toxin-g from Tityus serrulatus scorpion venom on gastric emptying in rats

The effect of toxin-gamma from Tityus serrulatus scorpion venom on the gastric emptying of liquids was studied in 176 young adult male Wistar rats (2-3 months of age) divided into subgroups of 8 animals each. Toxin-gamma was injected iv at doses of 25, 37.5, 50 or 100 mu g/kg and the effect on gastric emptying was assessed 30 min and 8 h later. A time-course study was also performed by injecting 50 pg of toxin-gamma/kg and measuring the effect on gastric emptying at times 0.25, 0.5, 1, 2, 4, 8, 24 and 48 h post-venom. Each envenomed animal was paired with its saline control and all received a saline test meal solution containing phenol red (60 mu g/ml) as a marker. Ten minutes after administering the test meal by gavage the animals were sacrificed and gastric retention was determined by measuring the residual marker concentration of the test meal. A significant delay in gastric emptying, at 30 min and 8 h post-venom, was observed only after 50 and 100 mu g of toxin-gamma/kg compared to control values. The responses to these two doses were significantly different after 8 h post-venom. Toxin-gamma (50 mu g/kg) significantly delayed the gastric emptying of liquids at all times studied, with a peak response at 4 h after toxin administration compared to control values. These results indicate that the iv injection of toxin-gamma may induce a rapid, intense and sustained inhibition of gastric emptying 0.25 to 48 h after envenomation.