Canatoxin, a proteic neurotoxin from Canavalia ensiformis seeds, raises circulating insulin levels and induces hypoglycemia in rats. The hyperinsulinemia produced by canatoxin (6 micrograms kg-1, 20 min; 108% of increase in female rats) was both time and dose dependent and lasted only about 30 min, while the fall in blood glucose levels (around 30%) was long lasting. The hyperinsulinemic response to canatoxin was greater in females (+108 +/- 18%) than males (+43 +/- 8%), but no difference was noted in the hypoglycemia. Pretreatment of rats with either naloxone, naltrexone, atropine or hexamethonium abolished both the hyperinsulinemia and the hypoglycemia. These data suggest that these phenomena are influenced by opioids and depend on parasympathetic stimulation.311131-6