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Biomedical subjects

N Rowland

Publications and source records attributed to N Rowland.

At least 73 records · Page 4Linked to original sources
PubMed1978

Hepatic versus cerebral origin of stimulus for feeding induced by 2-deoxy-d-glucose in rats.

Intravenous administration of 2-deoxy-D-glucose (2-DG), a competitive inhibitor of glucose utilization, increased the food intake of rats. Infusions of glucose or mannose abolished this effect, whereas equimolar fructose solutions did not affect 2-DG-induced feeding. Similar results were obtained when 2-DG and the hexoses were administered into the hepatic portal vein. These findings suggest that 2-DG elicits feeding due to glucoprivation at a site that is inaccessible to fructose. This site is likely to be in the brain, not the liver, because all three sugars can nourish peripheral tissue but only fructose cannot penetrate the blood-brain barrier. Moreover, 2-DG-induced feeding was abolished by intravenous infusion of beta-hydroxybutyrate, a substrate that can be oxidized by brain and other tissues but not by the liver.

Animals↗
PubMed1977

Homeostasis during hypoglycemia: central control of adrenal secretion and peripheral control of feeding.

Intravenous infusions of manose or B-hydroxybutyrate, metabolic fuels which can be oxidized by brain, abolished adrenal discharge of epinephrine in rats during insulin-induced hypoglycemia, whereas infusion of fructose, a sugar which does not cross the blood-brain barrier, did not. In contrast, increased feeding behavior during hypoglycemia was prevented both by the sugars and by B-hydroxybutyrate. Thus, while the sympathetic response during marked hypoglycemia may have been initiated by alterations in cerebal metabolism, the feeding response evidently was not, and a decrease in the utilization of glucose per se does not appear to be the critical stimulus in either case.

Animals↗
PubMed1977

Intravenous self-feeding: long-term regulation of energy balance in rats.

Rats learned to press a lever for intravenous self-injection of liquid diet during periods of several weeks when oral food was not available. The intakes were low but regulated, and were sufficient to balance energy expenditures at low body weight. Systemic receptors alone are thus adequate to motivate feeding behavior and meter the caloric yield of the intravenous injections.

Animals↗
PubMed1977

Bodyweight following lateral hypothalamic lesions: set point upset by glucose infusions.

Rats which had recovered to Stage 3 or 4 following lateral hypothalamic lesions maintained their bodyweight at a chronically lowered level when eating dry food. Continuous, long term intravenous and intragastric water infusions increased food intake and promoted a slow weight gain. Infusions of a similar volume of 30% glucose led to a small reduction in food intake and a rapid weight gain. Four rats doubled their weight during infusion; when the infusions were stopped all lost weight back to their starting level. These results are discussed in terms of the problems they present for lowered set point interpretations in such animals.

Animals↗
PubMed1977

Feeding and drinking interactions after acute butyrophenone administration.

The effects on feeding and drinking of various doses of droperidol, haloperidol and spiroperidol were studied in a number of paradigms. All three buryrophenones produced generally similar effects. After food deprivation, feeding was slightly increased at low doses but was decreased at the higher doses; the concomitant postprandial drinking was attenuated at all doses. Desalivate rats showed a marked attenuation of feeding (and prandial drinking) at low doses, but when wet mash was given instead of pellets and water a normal dose-response relationship was obtained. After water deprivation drinking was attenuated at all doses, and when food was also available during the drinking test the food intake was decreased in proportion to the drinking. Drinking was blocked more when food was present than in its absence. Insulin and 2-deoxyglucose induced feeding in sated rats was attenuated but not abolished by haloperidol. The findings are discussed relative to the role of activation and brain catecholamines in feeding and drinking.

Animals↗
PubMed1976

Circadian rhythms and partial recovery of regulatory drinking in rats after lateral hypothalamic lesions.

Rats that had recovered spontaneous ingestive behavior after lesions of the lateral hypothalamus were challenged with acute injections of hypertonic NaCl administered at different times during the day/night cycle. Following these injections, drinking was observed only during the nighttime. After morning injections the rats frequently waited until nightfall before drinking, whereas animals injected at night showed much shorter delays in the behavioral response; a similar nocturnal predominance of drinking was seen after food deprivation and in the ad-lib situation. Studies in blinded animals suggested that these effects were due to an endogenous circadian rhythm.

Age Factors↗
PubMed1976

Metering of fluid intake and determinants of ad libitum drinking in rats.

The contributions of homeostatis mechanisms to spontaneous drinking were assessed in a study of residual oral drinking under several conditions of exogenous water administration. Continuous and/or discontinuous infusiors were conducted for long periods with dry food present ad libitum. The routes of administration were intravenous (IV), intragastric (IG) through a nasopharyngeal catheter. All infusions reduced from noninfused levels, but the magnitude of that reduction was a function of both route and temporal characteristics. Continuous infusions were more effective via the IG route than IV, and a residual intake of about 10 ml/24 h presisted at even the highest infusion rates. Discontinuous meal-paired IV infusions suppressed mid- and postmeal drinking, consistent with the satisfaction of systemic needs induced by cry food intake. Meal-paired IG nasopharyngeal infusions competely suppressed drinking when the infusions exceeded base-line intake by only about 20%. In marked contrast, corresponding IG infusions through a direct fistula catheter were relatively ineffective. In all cases the decreases in drinking were not of a nonspecific nature beacuse food intake was unchanged. The discussion considers the different levels of metering involved and the time-varying (derivative) nature of the infusion if was suggested that there is a nonhomeostatic contribution to normal drinking.

Animals↗
PubMed1976

Metering of intravenous versus oral nutrients and regulation of energy balance.

Unrestrained rats received continuous and discontinuous intravenous infusions of nutritive substances over long periods, and the effects on energy regulation were examined. Oral food intake was decreased by all glucidic infusions, but by less than the theoretical (caloric) value of the infused substances. A residual oral food intake thus persisted when the energy needs were supplied intravenously, and rats with the greater residual intakes gained excessive body weight. The less nutritionally balanced the infusion, the less the reduction in food intake, which suggests that some of the residual oral feeding may be due to a specific appetite for missing elements. The reduction of oral intake became equal to the calories infused when exogenous insulin was coinfused, and results from discontinuous infusions showed a similar trend. A model for the metering of nutrients at the systemic level was proposed; only when substances are metabolized is there a direct effect on feeding control mechanisms.

Amino Acids↗
PubMed1975

Regulatory drinking in rats with permanent access to a bitter fluid source.

Male rats were given a quinine adulterated fluid as their sole source of liquid for over 60 days. After a latency of a few days, fluid intake stabilised at about 20 ml/day, with the water to food ratio close to 1.0 ml/g. Bodyweights fell to 90 percent of control levels (rats drinking unadulterated water). A battery of dipsogenic challenges was administered. Compared to controls, the ingestive responses during elevated ambient temperature, hyperosmotic salty food, after fluid deprivation, and to extracellular fluid depletion, were all attentuated. Drinking to acute NaCl injections was totally abolished. The intake of the adulterated fluid was near zero during food deprivation, and when a vegetable and fruit diet was available. Body fluid changes were suggestive of a net dehydration in the quinine drinking rats. Parallels with self intravenous drinking rats and rats recovered from lateral hypothalamic lesions were considered, and possible fundamental differences between natural and nonatural thirst stimuli.

Animals↗
PubMed1975

Metering of intravenously infused nutrients in VMH lesioned rats.

Rats were chronically implanted with lesioning electrodes in the ventromedial hypothalamus and with intracardiac catheters. The effects on ad lib oral food intake of a continuous intravenous infusion of glucose were studied both before and after lesioning. Before the lesion oral food intake was reduced by an average of 0.59 kcal per kcal infused. Postlesion the reduction of oral intake was correlated with the caloric value of the infusion, with a mean of 0.92 kcal per kcal. Rats with ventromedial hypothalamic lesions thus adjust their oral intakes in accordance with a systemically infused supplement. Further, the metering of systemically infused substrates actually appears to be more adequate after the lesion. This may be due to an exaggerated insulin release to systemic inputs which have bypassed the orogastric route and are thus unable to elicit preabsorptive endocrine reflexes.

Animals↗