Le developpement rapide de la consommation de produits alleges resulte de l'interference de plusieurs facteurs. L'utilisation de ces produits peut, dans certaines conditions, jouer un role dans la mai←trise du poids corporel. Mise au point des produits alleges. Le choix du produit est facilite par une composition et un etiquettage adequat

Le developpement rapide de la consommation de produits alleges resulte de l'interference de plusieurs facteurs. L'utilisation de ces produits peut, dans certaines conditions, jouer un role dans la mai←trise du poids corporel. Mise au point des produits alleges. Le choix du produit est facilite par une composition et un etiquettage adequat

Normal Wistar rats became hyperphagic and obese when presented with high-fat, high-sugar or “cafeteria” diets. This phenomenon could be due to the very palatability of the offered foods but a metabolic factor could be suspected. In an attempt to distinguish the effects of the nutritional characteristics from those of the sensory properties of food, a new cafeteria diet, the “isocafeteria” diet, was developed. It consists of a choice of foods of similar, well-balanced composition but varying in taste, smell and texture. It was confirmed that in normal Wistar rats, the high-fat and the traditional “cafeteria” diet led to extra-weight gain. It was demonstrated that the daily presentation of a new choice of the palatable foods which composed the “isocafeteria diet” led also to a sustained increase in food intake and to overweight. Variety and high palatability are per se sufficient factors to overcome regulatory mechanisms. It was shown that the metabolic efficiency of such a regimen was strikingly higher than those of high-fat and traditional cafeteria diets.

The magnitude of preabsorptive insulin release varies as a function of palatability. This suggests that the palatability-dependent rise in plasma insulin could accentuate the systemic stimulus to eat, which in turn could modulate the size of the meal. The present experiment was designed to test this hypothesis by investigating the ingestive responses of vagotomized rats, which no longer exhibit preabsorptive insulin release, when they are offered nutritionally identical diets differing only in their sensory characteristics. The presented foods were three forms of the rat's regular diet: unaltered, sweetened with sodium cyclamate or adulterated with quinine hydrochloride. It was shown that vagotomized rats ate exactly the same amount of the three diets in three different test-meals: without cephalic insulin release, meal size no longer seems to be modulated by oral cues.

A new test for completeness of vagotomy to the pancreas was developed. It is based upon the post-absorptive consequences of the absence of cephalic insulin secretion in vagotomized rats. Rats were divided into three groups: in group I, rats were submitted to a truncular vagotomy; in group II, rats underwent a selective gastric vagotomy; group III was a control group. The test was performed when operated rats had recovered from surgery. All rats were fasted from 9 a.m. to 14 a.m. At 14 a.m. (t=0) they were offered 1 ml of a 50% glucose solution and the small amount of urine secreted between t=10 and t=20 was tested for glucose using a reactive strip. Glucose was detected in rats of group I only. This test seems to be a good index of vagotomy to the pancreas; it is easy, inexpensive and non-terminal.

The autoradiographic method has been used in the Rat to map active regions in the olfactory bulb after a pulse of 14C-2-deoxyglucose with electrical stimulation of the lateral olfactory tract. The highest optical densities were found at the external plexiform, mitral, internal plexiform and granular layers; the lowest was found in the glomerular layer.

The possible role of centrifugal neural pathways in a feedback control of the olfactory input related to regulatory mechanisms of feeding behavior, has been investigated in rats. Bipolar electrodes were chronically and bilaterally implanted and multiunit discharges of the mitral cell layer recorded in unanesthetized rats. From the basal level of integrated activity, three types of responses to odor stimulations were considered: positive (enhanced), negative (inhibited) and null (unchanged). Rats were tested in a first group either hungry, after food deprivation or satiated, immediately after a single 2hr-daily meal. In a second group, they were tested either hungry under the effect of 20 U/kg body weight, of injected insulin, or satiated after their daily meal. In both groups, rats either hungry or satiated, were stimulated in test series by two different odors: (a) the odor of their familiar stock-diet; and, (b) a control odor: isoamyl acetate in the first group, citral in the second. Stimulated by the food odor, food-deprived and insulin treated rats exhibited positive responses. They exhibited, when satiated, significantly different negative responses. Stimulated by control odors, rats either hungry or satiated showed a same pattern of negative or null responses. Results are discussed in terms of a motivation dependant feedback control of the olfactory input in which the anatomically identified olfacto-hypothalamic loop is likely involved.