Effects of adrenoceptor blockers on the glycemic response to nicotine in thyroidectomised rats

The effect of adrenoceptor blockers on nicotine induced hyperglycemia were studied in fasted normal and thyroidectomised rats. Blood glucose was estimated using the modified glucose oxidase method. The control experiments consisted of sham operated rats with intact thyroid glands. Pre-treatment of the rats with either the alpha adrenoceptor blocker prazosin or the beta adrenoceptor blocker propranolol before intravenous injection of nicotine (50 micrograms/kg) significantly reduced the hyperglycemia induced by nicotine in normal rats, while a combination of propranolol and prazosin abolished nicotine induced hyperglycemia. In the thyroidectomised group, nicotine also caused hyperglycemia. However, the basal glucose level and peak of glycemic response were lowered compared to that in the control group. The results therefore seem to suggest that both alpha and beta adrenoceptors are involved in nicotine-induced hyperglycemia in the rat.