ABSTRACT
The effects of injecting or infusing neuropeptide Y (NPY) into the suprachiasmatic nucleus of rats on patterns of individual macronutrient and water intake were examined during the following 2 h and also across 12 and 24 h light/dark cycles. Increased total energy intake (218 and 170%) and energy intake from the dextrin/sucrose diet (499 and 247%) were observed in the 2 h following injection of 100 pmol NPY at early light and early dark, respectively, and in the following 24 h (total energy: 67%, dextrin/sucrose: 73%). Nocturnal casein energy intake was also increased (258%) following NPY injection. Continuous infusion of 10 pmol/h of NPY suppressed nocturnal total energy (36%) and dextrin/sucrose intake (36%) as well as 24 h energy intake from casein (43%). These results demonstrate divergent effects of NPY subsequent to different mode of administration.
Subject(s)
Eating/drug effects , Energy Intake/drug effects , Food Preferences/drug effects , Neuropeptide Y/pharmacology , Photoperiod , Suprachiasmatic Nucleus/drug effects , Animals , Darkness , Dietary Carbohydrates , Dietary Fats , Dietary Proteins , Eating/radiation effects , Energy Intake/radiation effects , Food Preferences/radiation effects , Light , Male , Rats , Rats, Wistar , Time FactorsABSTRACT
The effects of neuropeptide Y (NPY) injected into the hypothalamic suprachiasmatic nucleus (SCN) or the lateral cerebral ventricle (LCV) at four different time points of the day on the subsequent 2h food intake from three macronutrient rich diets were examined. Adult Wistar male rats on 12-12 h light-dark cycles received either saline or NPY (lOOpmol) through chronically implanted guide cannulas into the SCN or the LCV. The results show that NPY was effective at stimulating energy intake from the dextrin/sucrose diet when injected in the SCN after lights-on, and total energy intake when injected in the LCV before and after lights-on. This suggests that NPY is effective at altering nychthemeral variations in total energy and energy from dextrin/sucrose diets, but this modulation is specific to the site of administration.
ABSTRACT
This paper provides a procedure for estimating the maximal stationary metabolic rate (SMRmax) in free-moving rats. The SMRmax was estimated by simultaneously comparing energy expenditure with motor activity measured at 10 min intervals for 24 h. The SMRmax was close to but naturally higher than the resting metabolic rates determined by other conventional methods. The coefficient of variation for 3 consecutive days was below 3%. The ratio of SMRmax to daily minimum energy expenditure was 1.25 in young rats and 1.19 in adult rats. SMRmax is a useful key parameter for analyzing daily energy expenditure and behavior.
Subject(s)
Energy Metabolism , Animals , Male , Motor Activity , Rats , Rats, WistarABSTRACT
Compared were the light-dark pattern of absolute energy intake and macronutrient selection of male Wistar rats intracerebroventricularly infused with glucagon (5 ng/h) or saline for 7 days in a three-way selection of macronutrients. Glucagon infusion induced a decrease in 24 h and nocturnal energy intake, whereas no significant change in kcal intake accompanied vehicle infusion. The decrease in kcal intake was due to a suppression of nocturnal ingestion of carbohydrate. This parameter was left unaffected with central vehicle infusion. Glucagon-infused rats had a significantly lower body weight gain than those infused with vehicle. Our study supports the hypothesis of central glucagon's suppressive effect on food intake, but reveals that the latter reflects a lower disposition to eat carbohydrate during the dark phase. The present work emphasizes the role of glucagon in the circadian regulation of carbohydrate intake.
Subject(s)
Energy Intake/physiology , Food Preferences/physiology , Glucagon/physiology , Animals , Brain/physiology , Circadian Rhythm/physiology , Male , Rats , Rats, WistarABSTRACT
We investigated the effect of chronic infusion of neuropeptide Y (NPY) aimed at the hypothalamic suprachiasmatic nucleus (SCN) or the lateral cerebral ventricle (LCV) on food intake. The experiments were performed in adult male Wistar rats infused for 7 days with saline or NPY (10 and 100 pmol microliters-1 h-1) into the SCN (n = 18) or LCV (n = 17). Infusion of the lower dose of NPY in the SCN significantly decreased food intake, whereas infusion of the higher dose did not. There was no change in food intake specific to saline or either dose of NPY with infusion in the LCV. It is concluded that chronic infusion of NPY into the SCN at a dose of 10 pmol h-1 inhibits food intake in rats.
Subject(s)
Eating/drug effects , Neuropeptide Y/pharmacology , Suprachiasmatic Nucleus/physiology , Animals , Body Weight/drug effects , Depression, Chemical , Dose-Response Relationship, Drug , Injections , Injections, Intraventricular , Male , Neuropeptide Y/administration & dosage , Rats , Rats, WistarABSTRACT
In this paper, we presented a new procedure to determine daily minimum energy expenditure (MEE) in free-moving rats and mice kept in a chamber. Energy expenditure was measured for 23 h period and averaged every 10 min. Data were sorted in ascending order. MEE was estimated from the regression line with the smallest slope and the biggest intercept among the regression lines calculated between the sorted energy expenditure and the data ranking. Among three duplicate measurements in individual animals, MEE gave the smallest coefficient of variation (2.2%) as compared with actual measured-values: either the single lowest value (4.0%) or the average of the 6 lowest values (2.5%). Judging from diurnal patterns of energy expenditure and locomotor activity and from video tape observation of the rat's performance, it was confirmed that MEE represented an energy expenditure at rest. MEE decreased with fasting from days 1 to 5. MEE per body weight also declined with age, but stayed around 71-72 kcal/day/kg3/4 at 18 and 34 weeks of age in male Wistar rats. MEE in mice increased at lower ambient temperatures between 16 and 32 degrees C, but stayed fairly constant at the same temperature in repeated experiments. Thus, MEE estimated by the present regression procedure was highly reproducible and valid to determine the fundamental value of daily energy expenditure under free-moving conditions.
Subject(s)
Circadian Rhythm/physiology , Energy Metabolism/physiology , Locomotion/physiology , Aging/physiology , Analysis of Variance , Animals , Body Weight/physiology , Male , Mice , Mice, Inbred Strains , Rats , Rats, Wistar , Regression Analysis , TemperatureABSTRACT
We previously obtained evidence that in rats the neurons in the suprachiasmatic nucleus (SCN) receiving retinal neural inputs may be involved in the regulation of glucose metabolism. In this study we examined whether the SCN neurons containing vasoactive intestinal peptide (VIP)-like immunoreactive substance (VIP neurons) are involved in its regulation. We found that the hyperglycemic and hyperglucagonemic responses to intracranial injection of 2-deoxy-D-glucose (2DG) were synergistically enhanced by intracranial administration of VIP, and that these responses were significantly suppressed by treatment with anti-VIP antibody. These results suggest that VIP has a permissive effect on the hyperglycemic and hyperglucagonemic responses to 2DG, and thus that the VIP neurons in the SCN are probably involved in the regulation of glucose metabolism.
