THE EFFECTS OF INTRAGASTRIC HYPERALIMENTATION ON PAIR-FED RATS WITH VENTROMEDIAL HYPOTHALAMIC LESIONS
Abstract
The present study outlines the development and use of a novel pair feeding strategy to assess the contribution of an altered metabolic efficiency to the classical ventromedial hypothalamic (VMH) syndrome of obesity and hyperphagia. In addition, this protocol, employing intragastric hyperalimentation, is designed to address the related experimental issue of whether altered energy utilization serves as a physiological strategy employed in the defense of body weight and body fat. Female rats were equipped with intragastric catheters. One group of animals ingested a liquid diet orally (OR), while another group received the same diet intragastrically (IG). Half of the animals in these two groups were then given lesions of the ventromedial hypothalamic area (VW), and the other half were given sham lesions (SH). Food delivery to all animals was controlled by an intact, oral-feeding, ad libitum "master". The SHIG and VMIG animals were provided with 100% in excess of the master volume of diet ingested. The oral-fed rats, both lesioned (VMOR) and sham-lesioned (SHOR), were also allowed access to identical quantities of diet as the hyperalimented IG groups. Each experimental run lasted 36 days, during which food intake and body weight were monitored. At the end of 36 days, body composition and hormonal levels were assessed. The results indicate that, although both intact and VMH rats fed 200% of control intake became obese and were hyperinsulinemic, the rats with VMH lesions were relatively more obese than SHIG rats. In order to retain the identical level of energy above maintenance requirements (i.e. 140KJs of retained energy), VMH rats required 11% fewer calories of intake than shams. Further, the present experiment demonstrates that our intact, IG-fed rats did not evidence the caloric wastage that has been reported to occur in orally-fed rats which overeat a "cafeteria" diet.
Degree
Ph.D.
Subject Area
Physiological psychology
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