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

The effect of toxin-g from Tityus serrulatus scorpion venom on the gastric emptying of liquids was studied in 176 young adult male Wistar rats (2-3months of age) divided into subgroups of 8 animals each. Toxin-g was injected iv at doses of 25, 37.5, 50 or 100 µg/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 µg of toxin-g /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 µg/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 µg of toxin-g /kg compared to control values. The responses to these two doses were significantly different after 8 h post-venom. Toxin-g (50 µg/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-g may induce a rapid, intense and sustained inhibition of gastric emptying 0.25 to 48 h after envenomation.

Effect of Phoneutria nigriventer spider venom on gastric emptying in rats

The effect of Phoneutria nigriventer spider venom (PNV) on the gastric emptying of liquids was studied in 240 young adult Wistar rats (2-3 months of age) divided into subgroups of 8 animals each. The study was performed in 3 stages. Initially, PNV was injected into rats at doses of 0.19, 0.38 or 0.76 mg/kg and the effect on gastric emptying was assessed 30 min later. In the second stage, a time-course study was performed by injecting 0.76 mg PNV/kg and measuring the effect on gastric emptying 15, 60 and 120 min post-venom. In the last stage, in order to investigate the possible mechanisms of PNV influence on gastric emptying, one group of rats underwent subdiaphragmatic vagotomy and then received 0.76 mg PNV/kg while three other groups were pretreated iv with either prazosin (0.4 mg/kg), domperidone (1.0 mg/kg) or propranolol (0.6 mg/kg) and then given 0.38 or 0.76 mg PNV/kg. In this last stage, gastric retention was measured 30 min post-venom. Each animal received a saline test meal solution containing phenol red as a marker (60 microg/ml). Ten min after administering the test meal by gavage, gastric retention was determined by measuring the residual test meal marker concentration and the animals were sacrificed. PNV (0.76 mg/kg) provoked a significant delay in gastric emptying of liquids 15, 30 and 60 min after its administration. Propranolol partially interfered with gastric emptying in rats that had received 0.38 and 0.76 mg PNV/kg. Vagotomy and pretreatment of the rats with prazosin and domperidone had no effect. We conclude that the delay in the liquid gastric emptying observed in severely envenomed rats was probably due, at least in part, to a venom-stimulated release of catecholamines which inhibited gastric motility by activating smooth muscle beta-adrenergic receptors.