A kappa opiate agonist, U50,488H, enhances energy expenditure in rats.

The effect of U50,488H (a selective kappa opiate agonist) on oxygen consumption was measured in either resting and free-moving rats. In both states, U50,488H provokes an increase in oxygen consumption. In resting rats, the increase occurs at lower doses than in free-moving rats.

Permanent administration of d-fenfluramine in rats: paradoxical effects.

In order to test the hypothesis of Levitzky that d-fenfluramine (d-F) acts by modifying the ponderal set-point, we compared the effects of a permanent infusion of d-F on food intake and body weight (BW). The effect on the weight persisted as long as the infusion; the clear-cut anorectic effect lasted only a few days. This paradox is compatible with the set-point hypothesis.

The effects of a constant T3 level and thermoneutrality in diet-induced hyperphagia.

Rats were thyroidectomized, then fitted with a miniosmotic pump infusing T3, thereby assuring a constant circulating level of T3. After a ten-day recovery period, they were submitted either to a chow or to a cafeteria diet. Body weight, food intake, and energy expenditure were recorded during a thirty day period.

Decreased insulin binding to adipocytes precedes both hyperinsulinemia and decreased insulin binding to erythrocytes in cafeteria-fed rats.

The relationship between food intake, obesity, insulin binding to adipocytes and erythrocytes, plasma insulin and plasma glucose was studied in an animal model of nutritional obesity--'the cafeteria-fed rats'--after 3 days, 10 days, and 3 weeks of cafeteria feeding. The antilipolytic effect of insulin was also studied. The cafeteria-fed rats ate more carbohydrates after 3 days of diet, while from the 10th day, as previously found, they ate about the same amount of carbohydrates but more lipids and increased in weight.

Action of naltrexone on the sexual impairment of obese cafeteria rats.

Two experiments were performed to explore 1) the sexual behavior of male obese cafeteria rats, 2) a possible role of endogenous opiates in the regulation of their sexual behavior. In obese cafeteria rats the proportion of ejaculators and the number of ejaculations per hour were significantly lower compared to controls. Naltrexone provoked an increase in the number of ejaculations/h both in control and cafeteria rats due to an induction of copulatory behavior in sexually inactive rats.