Effect of cholinergic and adrenergic stimulation of the subfornical organ on water intake

Cholinergic and adrenergic agonists and antagonists were injected directly into the subfornical organ (SFO), via implanted cannulae, and the volume of water ingested was recorded over a period of 1 hour after injection. Application of 2 nmol carbachol caused intense water intake in 100% of the animals (8.78±0.61 ml), with a very short intake latency. When the 2 nmol carbachol dose was preceded by increased doses of atropine, a progressive reduction in water intake was observed, with complete blockage of the thirst-inducing response to carbachol at the 20 nmol dose level with atropine. Followed by several doses of hexamethonium, the water intake caused by application of 2 nmol carbachol was reduced, although the response was not totally blocked. Injection of 80 nmol of nicotine had a significant thirst-inducing inducing effect in 50% of the animals studied (1.06±0.18 ml) and increase in water intake was further reduced by application of increased doses of hexamethonium. Raising the dose levels of noradrenaline into th SFO caused an increase in water intake although to a lesser degree than was observed after carbachol injection. When the 40 nmol dose of noradrenaline was preceded by increased doses of propranolol (5 to 40 nmol), there was a gradual reduction in water intake, with total blockage at the 40 nmol dose. Application of phentolamine in doses of 10 to 80 nmol caused no reduction in water intake after 40 nmol of noradrenaline. Application of isoproterenol at doses from 20 to 160 nmol into the SFO caused a dosedependent increase in water intake which was blocked by previous applications of propranolol. These results support the hypothesis that the water intake caused by chemical stimulation of the SFO is mainly due to muscarinic cholinergic receptors, although the influence of nicotinic receptors or participation of adrenergic mediation should not be ruled out. © 1984.

Effect of ambient temperature and thyroid hormones on food intake by pigs

Food intake and plasma thyroid hormone levels (T4 and T3) were higher in pigs acclimated to cold (12°) than hot (32°) environments. The exposure of cold pigs to hot ambient temperature decreased food intake and plasma T4 and T3, whereas for hot acclimated animals the change in ambient temperature (from 32 to 12° C) increased food intake and plasma thyroid hormone levels, but the new steady state level of food intake was reached only after 96 hr of temperature transfer despite the rapid change in plasma levels of thyroid hormones. Cold-acclimated pigs, when transferred to a hot environment after thyroidectomy, also reduced food intake, but hot pigs shifted to cold ambient temperature after thyroidectomy did not significantly increase food ingestion. The results of this experiment suggest that food intake adjustment depends on the previous living temperature and that thyroid hormones seem to play an important role in increasing the metabolically active mass that probably sustains the new steady state level of food intake, particularly in a cold environment.

Effect of air temperature and humidity on ingestive behaviour of sheep

Thirty-two Polwarth ewes, of ages up to 1 year, were observed in a climatic chamber (24 to 45° C) for eight periods of 5 h each. The observations were made through a window in the chamber wall. All animals were observed four times, then shorn and observed four times again. The animals were given weighed quantities of water and feed consisting of commercial concentrate plus Rhodes grass (Chloris gayana) hay. The water and feed remaining after 5 h of observation were weighed. The following traits were analysed: time eating hay (TEH), time eating concentrate (TEC), time drinking water (TDW), weight of hay eaten (WHE), weight of concentrate eaten (WCE), volume of ingested water (VIW), ruminating time standing up (RTS), ruminating time lying down (RTL), idling time standing up (ITS), and idling time lying down (ITL). Shearing had a significant effect for all traits except ITS. Shearing resulted in higher values for all traits except for ITS and ITL. Ingestion of hay (TEH and WHE) decreased with increased air temperature and humidity, while the ingestion of concentrate (TEC) and WHE) and water (TDW and VIW) increased. Rumination decreased with increased air temperature and humidity, and was higher in shorn than in unshorn sheep. © 1992 International Society of Biometeorology.

On a possible dual role for central noradrenaline in the control of hydromineral fluid intake

Noradrenaline (NOR) is a neurotransmitter presenl in the central nervous system which is related to the control of ingestive behavior of food and fluids. We describe here the relationship between NOR and intake of water and NaCl solution, fluids that are essential for a normal body fluid electrolytic balance. Central NOR has an inhibitory effect on fluid intake, but it either induces or not alterations in food intake. Several ways of inducing water intake, such as water deprivation, meal-associated water intake, administration of angiotensinergic, cholinergic or beta-adrenergic agonists, or administration of hyperosmotic solutions, are inhibited by alpha-adrenergic agonists. Need-induced sodium intake by sodium-depleted animals is also inhibited by alpha-adrenergic agonists. NOR can also facilitate fluid intake. Water intake is elicited by NOR and the integrity of central noradrenergic systems is necessary for a normal expression of water or salt intake in dehydrated animals. The angiotensinergic component of either behavior apparently depends on a central noradrenergic system. NOR probably facililates fluid intake by acting on postsynaptic receptors, but we do not know how it inhibits fluid infake. The inhibitory and facilitatory effects of NOR on ingestive behavior suggest a dual role for this neurotransmitter in the control of hydromineral fluid intake.

Effect of nicotinic stimulation of the amygdaloid complex on water and sodium chloride intake

We studied the nicotine stimulation of the amygdaloid complex (AMG) on sodium and water intake in satiated and water-deprived rats. Nicotine produced no change in sodium or water intake in satiated animals when injected directly into the AMG. In water-deprived animals, nicotine injected into the AMG (basolateral nuclei) only blocked sodium chloride intake. We have previously demontrated that carbachol inhibits water and sodium intake in both satiated and water-deprived animals injected into the AMG. Injection of hexamethonium into the AMG totally blocked water intake in satiated and water-deprived animals. Hexamethonium injected into the AMG prior to nicotine produced no change in sodium intake. Thus, the present data suggest that sodium and water intake are mediated by a specific population of cholinoceptive neurons in the amygdaloid complex.

Commissural nucleus of the solitary tract lesions reduce food intake and body weight gain in rats

This study investigated the effects of an electrolytic lesion of the commissural subnucleus of the nucleus of the solitary tract (commNTS) on bodyweight, daily food and water intake, and plasma glucose and insulin in rats. In the first 6 days following brain surgery, commNTS lesioned rats reduced daily food intake by 80% compared to rats with sham lesions. After this period rats with lesions of commNTS started recovering food intake, but intake remained significantly reduced until the 12th day after surgery. A reduction in body weight was observed 4 days after surgery and reached a maximum on the 12th day. After this, a partial recovery of body weight was observed, but weight remained significantly reduced compared to weights of rats with sham lesions through the conclusion of the study. Food intake and body weight gain in other rats with partial lesions of the commNTS or with lesions outside the commNTS did not differ from rats with sham lesions with regard to those variables. Daily water intake and plasma glucose and insulin were not changed by the commNTS lesions. These results suggest that commNTS is involved with mechanisms that control food intake and body weight in rats.

Effect of adrenergic stimulation of the amygdaloid complex on water intake

The effect of noradrenaline, isoproterenol, phentolamine and propranolol, injected into the basolateral nuclei of the amygdala on water intake, was investigated in male Holtzman rats. The injection of noradrenaline (40 nmol) into the amygdaloid complex (AC) of satiated rats produced no change in water intake (0.05 ± 0.03 ml/1 hour). The injection of isoproterenol (40 nmol) produced an increase in water intake in sedated rats (1.93 ± 0.23 ml/1 hour). Noradrenaline injected into the AC produced a decrease in water intake in deprived rats (0.40 ± 0.19 ml/1 hour). The injection of isoproterenol into the AC of deprived rats produced no change in water intake in comparison with control (11.65 ± 1.02 and 10.92 ± 0.88 ml/1 hour, respectively). When compared with control values, phentolamine injected prior to noradrenaline blocked the inhibitory effect of noradrenaline on water intake in deprived rats (10.40 ± 1.31 ml/1 hour). Propranolol blocked the effect of isoproterenol in satiated rats (0.85 ± 0.49 ml/1 hour) and also blocked the water intake induced by deprivation (0.53 ± 0.38 ml/1 hour). In satiated and deprived animals the injection of phentolamine before hexamethonium blocked the inhibitory effect of hexamethonium on water intake. In satiated animals, when hexamethonium was injected alone, water intake was 0.39 ± 0.25 ml/1 hour and when hexamethonium was injected with phentolamine, water intake was 1.04 ± 0.3 ml/1 hour. In deprived animals, hexamethonium alone blocked water intake (0.40 ± 0.17 ml/1 hour) and when injected with phentolamine it elicited an intake of 9.7 ± 1.8 ml/1 hour. these results clearly demonstrate the participation of catecholaminergic receptors of the AC in the regulation of water intake.

Preoptic-periventricular tissue (AV3V): central cholinergic-induced hydromineral and cardiovascular responses, and salt intake.

The periventricular tissue of the anterior ventral portion of the third ventricle (AV3V) is an important area for the control of hydromineral balance and of cardiovascular function. The present work discusses the importance of the integrity of the AV3V for multiple responses to central cholinergic activation (water intake, hypertension, natriuresis, salivation) and for the control of salt intake.

Multifactorial control of water and saline intake: Role of α2-adrenoceptors

Water and saline intake is controlled by several mechanisms activated during dehydration. Some mechanisms, such as the production of angiotensin II and unloading of cardiovascular receptors, activate both behaviors, while others, such as the increase in blood osmolality or sodium concentration, activate water, but inhibit saline intake. Aldosterone probably activates only saline intake. Clonidine, anα2-adrenergic agonist, inhibits water and saline intake induced by these mechanisms. One model to describe the interactions between these multiple mechanisms is a wire-block diagram, where the brain circuit that controls each intake is represented by a summing point of its respective inhibiting and activating factors. The α2-adrenoceptors constitute an inhibitory factor common to both summing points.

Effects of the alpha antagonists and agonists injected into the lateral hypothalamus on the water and sodium intake induced by angiotensin II injection into the subfornical organ

The subfornical organ (SFO) and the lateral hypothalamus (LH) have been shown to be important for the central action of angiotensin II (ANG II) on water and salt regulation. Several anatomical findings have demonstrated neural connections between the SFO and the LH. The present experiments were conducted to investigate the role of the α-adrenergic antagonists and agonists injected into the LH on the water and salt intake elicited by injections of ANG II into the SFO. Prazosin (an α1-adrenergic antagonist) injected into the LH increased the salt ingestion, whereas yohimbine (an α2-adrenergic antagonist) and propranolol (a β-adrenergic antagonist) antagonized the salt ingestion induced by administration of ANG II into the SFO. Previous administration of clonidine (an α2-adrenergic agonist) or noradrenaline into the LH increased, whereas pretreatment with phenylephrine decreased the sodium intake induced by injection of ANG II into the SFO. Previous treatment with prazosin and propranolol reduced the water intake induced by ANG II. Phenylephrine increased the dipsogenic responses produced by ANG II, whereas previous treatment with clonidine injected into the LH reduced the water intake induced by ANG II administration into the SFO. The LH involvement with SFO on the excitatory and inhibitory mechanisms related to water and sodium intake is suggested.

Desempenho e Digestibilidade in vivo de Cordeiros Alimentados com Dietas Contendo Canola em Grão Integral em Diferentes Formas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Utilização de NaCl no suplemento como alternativa para viabilizar o sistema de alimentação de bezerros em creep-feeding

Thirty two Canchim suckling calves, maintained on rotational grazing system of Brachiaria brizantha cv. Marandu, were divided in three groups corresponding to three evaluated treatments: control (without creep-feeding); SAL5 (addition of 5% of NaCl to concentrate fed in creep-feeding); and SAL10 (addition of 10% of NaCl to concentrate fed in creep-feeding). Feeding in a creep-feeding system lasted 90 days, divided in three subperiods of 30 days. The body weight gain was greater in the subperiods 1 and 2 for SAL10 and SAL5 treatments, respectively. There were no differences in the third subperiod and, in the overall period, the SAL10 treatment (0.91 kg.animal-1.day-1) was better than control treatment (0.81 kg,animal-1.day-1). The monthly remuneration provided by the treatments SAL5 e SAL10 related to the control group were-12.5 and 6.0%, respectively. The body weight differentials at weaning, compared to the control group, for creep-feeding provide a monthly net profit of 0, 0.6, 1.2, and 6.0% should be 10.8, 11.0, 11.2, and 12.8 kg.animal-1 for SAL5 and 7.6, 7.7, 7.8, and 9.0 kg.animal-1 for SAL10. It was concluded that the limited supplement intake in creep-feeding was necessary to obtain economic viability.

Efeito de estratégia de suplementação com concentrado no desempenho de cabras mestiças Saanen, em dois sistemas de produção

The experiment was carried out to evaluate the performances of cross breed Saanen dairy goats submitted to two strategies of supplementation with concentrate 30% of daily requirements in net energy (NRC, 1981) supplied by concentrate, from third week until the end of lactation (ESC. 1) or 60% of requirements from the 3rd to the 13th week of lactation and 15% from 14th until the end of lactation (ESC.2); and evaluate the animal response to these strategies of supplementation with concentrate in a semi-confined or pasture systems. Thirty one animals were used in a completely randomized design. The system of production affected the total intake of concentrate and total milk production; at pasture system the values for these two variables were higher. The supplementation with concentrate affected the total intake of concentrate and total production of milk and the relation of milk/consumption of concentrate. The highest value for relation of milk/consumption of concentrate and the least for the total consumption of concentrate were obtained at ESC. 1. Body weight affected of the system of production, resulting in a higher value to the system of pasture. Weight and body condition had different responses to he supplementation with concentrate according to the system of production. The semi-confined system ESC.2 resulted in a higher value to the body condition; the body weight was no affected. At pasture system the highest values for weight and body condition were obtained in the supplementation with concentrate ESC. 1. Reproductive parameters did not affect supplementation with concentrate and system of production.

Acute reduction in serum progesterone concentrations after feed intake in dairy cows

This study tested the hypothesis that high feed consumption will acutely decrease circulating progesterone concentrations. In the first experiment, a Latin Square design was used to test whether feeding pattern would alter circulating progesterone in pregnant lactating Holstein cows (n = 12). Feed was removed for 12 h before the experiment and cows were then either fed 100% of the total mixed ration (TMR), 50% of TMR every 12 h, 25% of TMR every 6 h, or left unfed for an additional 12 h. Blood samples were taken every hour for 24 h. Provision of 100 or 50% of TMR decreased circulating progesterone by 1 h after feeding and progesterone remained depressed until 8-9 h after feeding. Feeding 25% of TMR did not reduce circulating progesterone concentrations. Experiment 2 used a crossover design to measure the effect of acute feeding on circulating progesterone and LH concentrations during delivery of a constant amount of exogenous progesterone (Eazi-Breed CIDRs) in lactating Holstein cows (n = 8) and nonpregnant dry Holstein cows (n = 6). Blood samples were taken every 15 min for 8 h. There was no change in serum progesterone during the 8 h treatment period in unfed cows; however, feeding decreased (P < 0.05) circulating progesterone between 2 and 6 h after feeding. In lactating cows, feeding increased mean LH (P < 0.05). There were more LH pulses (P = 0.01) in lactating than nonlactating cows. Thus, acute feeding reduced circulating progesterone in pregnant lactating cows apparently due to an increase in progesterone metabolism. Interestingly, feeding multiple smaller meals eliminated the acute effect of feeding on circulating progesterone. © 2003 Published by Elsevier B.V.