1. The present study was designed to characterize sex-related canatoxin-induced blood glucose alterations in rats. 2. Chronic administration of canatoxin (50 mU, ip, daily for 3 days) induced hypoglycemia in female rats (N = 6) (-36.54 +/- 3.24%, P less than 0.05). The response of pregnant rats (N = 8) was similar to that observed for male rats (+29.57 +/- 4.70%). 3. Administration of canatoxin did not modify blood glucose levels of gonadectomized male or female rats. Similarly, pretreatment of intact male or female rats with human chorionic gonadotropin (40 IU/kg, im) blocked the effect of canatoxin on blood glucose levels. 4. Gonadal steroid replacement (testosterone, 10 mg/kg, im) for gonadectomized male rats did not reverse the inhibition of canatoxin-induced blood glucose alterations, whereas pretreatment of intact female rats (N = 6) with testosterone (10 mg/kg, im) significantly attenuated the canatoxin-induced hypoglycemia. 5. These data indicate that the blood glucose alterations produced by canatoxin in rats are under hormonal regulation.221507-13