Date of Award

1968

Degree Type

Thesis

Degree Name

Master of Science in Zoology

Department

Zoology

First Advisor

Robert W. Harrison

Abstract

Mice of the KC strain can survive injections up to 300 units of insulin as compared to the maximum 30-50 units tolerated by normal BUB mice. This resistance is inherited. The KC mice are able to survive the hypoglycemia by maintaining their blood sugar level just above that which produces convulsions. Previous work had suggested that an increased rate 0£ food consumption supplied the carbohydrate necessary to overcome the hypoglycemia.

Current theories on the mechanism of hunger drive emphasize the role played by the hypothalamic reeding centers. The best understood centers are the lateral feeding center and the ventromedial satiety center. Evidence has accumulated to show that the ventromedial center is a glucoreceptor which inhibits the activity of the lateral nucleus during periods of high blood glucose.

To test the hypothesis that the hypothalamic feeding centers play a role in the insulin resistance, the ventromedial nucleus was destroyed by aurothioglucose. This compound has been demonstrated to be relatively specific for the satiety center, and its administration results in a hyperphagia aid obesity due to the unchecked activity of the lateral center.

The amount of food consumed was measured daily for a period of ten days, and as expected the aurothioglucose-treated mice exhibited a hyperphagia. Of the remaining groups the tolerant strain ate more per day than the intolerant. In the period after insulin injection, I however, the intolerant mice ate at the fastest rate and the tolerant mice just slightly less. The tolerant mice rendered hyperphagic and obese by aurothioglucose exhibited a suppression of food consumption in response to insulin.

When these findings are related to the proposed mechanism of insulin tolerance, it becomes questionable that the amount of food consumed is the sole determinant of survival after insulin stress. Also discovered is the possibility that this procedure may be of value in investigating the role played by feeding centers not located in the ventromedial nucleus and not sensitive to glucose or aurothioglucose.

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