Injections into the duodenum and the induction of satiety in the rat.

Abstract

A number of ways in which the intestine might participate in the induction of satiety have been examined using direct intestinal injections to alter the contents of the duodenum and then observing the effect on subsequent food intake over a 2K-hr period. The injection of either bulk or hypertonic solutions (NaCl or glucose) into the duodenum suppressed food intake. The injection of substantial amounts of food did not have an effect greater than that caused by equivalent amounts of nonnutritive bulk and the injection of acid material did not suppress eating more than basic material. These results suggest that bulk and osmotic pressure in the duodenum may initiate physiological changes which can ultimately participate in the regulation of meal size but that metabolites, duodenal hormones, and specific dynamic action do not. With the gastrointestinal system intact, the flow of material from the stomach to the intestine would be sufficiently slow that neither changes in duodenal bulk nor osmotic pressure would be involved in the regulation of meal size. When the stomach is partially removed or denervated, the rate of passage of food into the duodenum may increase enough so that osmotic and bulk signals originating in the duodenum would help to regulate meal size.

Control of food intake during continuous injection of glucose into the upper duodenum and the upper ileum of rats

“…Our results indicate that the reduction in mean daily voluntary food intake in the present experi-· ment, which is concerned with the day-to-day control of food intake, is due to the caloric content of the injected nutrients and not due to an osmotic or bulk effect which elicits a satiety response during a single meal (Campbell & Davies, 1974a, b;Ehman et al, 1971;Yin & Tsai, 1973). These findings are compatible with those of Snowdon (1975) showing that daily injections of energy contributing nutrients into the duodenum of rats result in a compensatory decrease of voluntary food intake.…”

“…The other approach consists of injecting various substances directly into GI tracts of hungry animals. In these experiments, injection of glucose into the stomach or the duodenum prior to a meal of free-feeding animals, as well as those feeding under various schedules, reduced the size of the ensuing meal (Campbell & Davis, 1974a, b;Ehman, Albert, & Jamieson, 1971;Novin, Sanderson, & Vanderweele, 1974;Yin & Tsai, 1973). Injection of solutions of NaC!, equi-osmotic to glucose (Yin & Tsai, 1973;Ehman et aI., 1971) or urea (Campbell & Davis, 1974a, b) as well as injection of nonnutritive bulk (Ehman et aI., 1971) also suppressed food intake.…”

SAPID Solutions and Food Intake in Repeated Dehydration and Rehydration Periods in Rats

“…In dehydrated rats, the intake of a conspicuous amount of dry food might further compromise osmolality and body fluid balance (Adolph, 1947;Lal & Zabik, 1970). Moreover, the small amount of food eaten and the NaCl solution drunk might both induce hypertonicity in the gastrointestinal tract producing a reduction in hunger (Hunt & Pathak, 1960;Ehman et al 1972;Yin & Tsai, 1973). The NaCl solution may assume two types of reinforcing stimulations, fluidity and saltiness, that may assume great reward value in restoring body fluid osmolality and [Na + ] promptly.…”

“…(a) Energy: rats ate food to recover body weight lost during periods of dehydration. (b) Osmotic pressure: the intake of quinine, HCl, or water may cause a hypotonicity in the intestinal tract and, as a consequence, increased hunger (Hunt & Pathak, 1960;Ehman et al 1972;Yin & Tsai, 1973). One way in which animals can prevent over-dilution when drinking water or a non-electrolytic solution to restore a body fluid deficit is by eating (Rolls & Rolls, 1982).…”

Feeding pattern of rabbits following intraduodenal glucose infusion as a function of caloric load, fasting interval, and vagal denervation

“…Although some investigations have failed to observe nutrient-specific satiety following glucose infusion into the alimentary tract (Ehman, Albert, & Jamieson, 1971; Glick, 1979;Yin & Tsai, 1973), the use of long-fasted animals may have been a reason for the absence of satiety, since the depression in feeding produced by intraduodenal glucose infusion in free-feeding rabbits was absent following a fast (Novin et aI., 1974). VanderWeele, Skoog, and Novin (1976) demonstrated that intraduodenal glucose administration decreased feeding in freefeeding rabbits but not in rabbits fasted for even as short a period as 2 h. The magnitude of the glucose load also plays a very important role in determining its modulatory influence on feeding, since a small duodenal infusion (3.5 mIl kg BW) of 5% glucose decreased food intake in free-feeding rabbits, where~s a larger load (10.5 mIlkg BW) of 5070 glucose actually intake to caloric availability (Booth & Jarman, 1976;Friedman & Stricker, 1976).…”