Inhibition of gastric emptying and intestinal transit in anesthetized ratsby a Tityus serrulatus scorpion toxin

The effects of a fraction (T1) of Tityus serrulatus scorpion venom prepared by gel filtration on gastric emptying and small intestinal transit were in vestigated in male Wistar rats, Fasted animals were anesthetized with ureth ane, submitted to tracheal intubation and right jugular vein cannulation. S corpion toxin (250 mu g/kg) or saline was injected iv and 1 h later a bolus of saline (1.0 ml/100 g) labeled with (99m)technetium-phytate (10 MBq) was administered by gavage, After 15 min, animals were sacrificed and the radi oactivity remaining in the stomach was determined. Intestinal transit was e valuated by instillation of a technetium-labeled saline bolus (1.0 mi) thro ugh a cannula previously implanted in the duodenum. After 60 min, the progr ession of the marker throughout 7 consecutive gut segments was estimated by the geometric center method, Gastric retention of the liquid test, meal in rats injected with scorpion toxin (median: 88%; range: 52-95%) was signifi cantly higher (P<0.02) than in controls (54%; 21-76%), an effect which was not modified by gastric secretion blockade with ranitidine. The progression of the isotope marker throughout the small intestine was significantly slo wer (P<0.05) in rats treated with toxin (1.2; 1.0-2.5) than in control anim als (2.3; 1.0-3.2). Inhibition of both gastric emptying and intestinal tran sit in rats injected with scorpion toxin suggests an increased resistance t o aboral flow, which might be caused by abnormal neurotransmitter release o r by the local effects of venom on smooth muscle cells.