Insulin tolerance test and glucose tolerance test

Rats were fasted for 4 h prior to the ITT conducted in the afternoon and overnight prior to the GTT conducted in the morning. After the fast, the rats were weighed and placed in a clear restraint tube which allowed easy access to the tail for blood sampling. The tip of the tail (1 mm) was cut with a scalpel for the baseline sample. Blood was collected from this same point throughout the test, without needing to cut the tail again. Approximately 2 µl of blood per read was analyzed for glucose content using the Alphatrak analyzer and strips (Zoetis, Florham Park, NJ). Insulin or glucose was injected into the peritoneal cavity after the baseline glucose measurement and blood glucose was measured at the following time points post injection: 15, 30, 45, 60, 75, 90, 105 and 120 min. Doses of insulin and glucose were dependent on the glucose status of the animals and were 0.75 IU kg⁻¹ and 1.50 mg g⁻¹, respectively.