DISCRIMINATION OF INSULIN-PRODUCED HYPOGLYCEMIA IN RATS

Hypoglycemia is an abnormal state that can be induced by administering insulin to a fasting animal. Rats were trained to discriminate the no rmal state of euglycemia from the hypoglycemia produced by injection o f 6 units/kg insulin. A drug discrimination procedure was used with a two-lever operant response. Insulin or water injected 25 min prior to the operant sessions determined whether left or right lever presses we re reinforced. During 40 training sessions, reliable discrimination of the insulin-produced cue developed. After insulin injection, mean blo od glucose levels dropped to about 75% of preinjection values. At 12 m in postinsulin injection, prior to the development of hypoglycemia, no ninsulin responses were made. Noninsulin responses were also made afte r injection with 800 mg/kg ethanol, indicating that a novel interocept ive state did not substitute for the insulin-produced cue. Insulin inj ections produced less severe hypoglycemia in less food-deprived rats, which again gave noninsulin responses. Animals can be trained to recog nize the insulin-produced state, which presumably involves hypoglycemi a, and/or counterregulatory processes evoked in response to the drop i n blood glucose.