The beneficial effects of early short-term exercise in the offspring of obese mothers are accompanied by alterations in the hypothalamic gene expression of appetite regulators and FTO (fat mass and obesity associated) gene.

Maternal overnutrition is implicated in the development of adult metabolic disease, and has been shown to alter the expression of genes involved in energy homeostasis. In the present study, we aimed to test whether a short period of voluntary exercise, followed by a sedentary period, would regulate hypothalamic markers involved in appetite. Adult female Sprague-Dawley rats were fed either normal chow or high-fat diet (HFD) ad lib. for 5 weeks, mated and continued on their assigned diet during gestation/lactation. At weaning males, were separated into chow or HFD groups; half were exercised (running wheels), whereas the remainder were sedentary. At week 10, wheels were removed and rats remained sedentary for 5 weeks, prior to tissue collection. Maternal obesity increased offspring adiposity at 15 weeks and this was exacerbated by postnatal HFD (P < 0.05). Body weight and fat mass were reduced in offspring of obese mothers if they exercised, and this was maintained even after 5 weeks without exercise. At 15 weeks, fasting plasma insulin, leptin and triglyceride concentrations were significantly reduced by exercise in offspring of lean and obese mothers consuming chow, with little benefit in those consuming HFD. Hypothalamic mRNA expression of pro-opiomelanocortin was increased by exercise but only in offspring of lean mothers. Exercise reduced hypothalamic FTO (fat mass and obesity associated) mRNA in offspring of lean dams regardless of diet. A short period of exercise early in life had lasting beneficial effects on body weight, adiposity and hormone profile of male offspring from obese and lean dams, despite being followed by a period of inactivity. The effects of exercise on hypothalamic appetite regulators were more marked in offspring of lean dams.

Voluntary post weaning exercise restores metabolic homeostasis in offspring of obese rats.

AIM: Physical exercise reduces obesity, insulin resistance and dyslipidemia. We previously found that maternal obesity alters central appetite circuits and contributes to increased adiposity, glucose intolerance and metabolic disease in offspring. Here we hypothesized that voluntary exercise would ameliorate the adverse metabolic effects of maternal obesity on offspring. METHODS AND RESULTS: Sprague-Dawley females fed chow (C) or high-fat diet HFD (H) were mated. Female offspring from C dams were weaned onto chow (CC); those from H dams recieved chow (HC) or HFD (HH). Half of each group was provided with running wheels (CC(EX), HC(EX), HH(EX); n=10-12). Maternal obesity increased body weight (12%), adiposity, plasma lipids and induced glucose intolerance (HC vs CC; P<0.05). These were exaggerated by postweaning HFD (HH vs HC; P<0.01), showed doubled energy intake, a 37% increase in body weight, insulin resistance and glucose intolerance (HH vs HC; P<0.01). Exercise reduced fat mass, plasma lipids, HOMA and fasting glucose in HC(EX) (vs HC; P<0.05) and HH(EX) (vs HH; P<0.01). Values in HC(EX) were indistinguishable from CC, however in HH(EX) these metabolic parameters remained higher than the sedentary HC and CC rats (P<0.01). mRNA expression of hypothalamic pro-opiomelanocortin, and adipose tumour necrosis factor α and 11ß-hydroxysteroid dehydrogenase type 1 were reduced by exercise in HH(EX) (vs HH; P<0.05). CONCLUSION: While voluntary exercise almost completely reversed the metabolic effects of maternal obesity in chow fed offspring, it did not fully attenuate the increased adiposity, glucose intolerance and insulin resistance in offspring weaned onto HFD.

Leucine improves glucose and lipid status in offspring from obese dams, dependent on diet type, but not caloric intake.

Previously, we showed that offspring from obese rat dams were hyperphagic, with increased adiposity, hyperlipidaemia and glucose intolerance associated with increased orexigenic neuropeptide expression after fasting. Mammalian target of rapamycin (mTOR) can inhibit food intake through a hypothalamic action. As we previously showed that maternal obesity down-regulated hypothalamic mTOR, in the present study, we hypothesised that dietary leucine supplementation would activate hypothalamic mTOR to reduce food intake, thus limiting metabolic disorders in offspring from obese dams, regardless of postweaning diet. Obesity was induced in Sprague-Dawley females by high-fat diet (HFD) for 5 weeks before mating, throughout gestation and lactation. Male pups from HFD-fed mothers were weaned onto chow or HFD; within each dietary group, half were supplied with leucine via drinking water (1.5%) versus water control for 10 weeks. Those from chow-fed mothers were fed chow and water. Maternal obesity led to increased adiposity in chow-fed offspring. Postweaning HFD consumption exaggerated adiposity, hyperglycaemia, hyperinsulinaemia and hyperlipidaemia. Supplementation with leucine doubled leucine intake and increased hypothalamic mTOR activation; however, appetite regulation was not affected. A reduction in blood lipid levels was observed in offspring regardless of diet, as well as improved glucose tolerance in HFD-fed rats. In HFD-fed rats, up-regulated carnitine palmitoyl-transferase-1 and peroxisome-proliferator-activated receptor-γ coactivator-1α in muscle and glucose transporter 4 in fat suggested that leucine improved peripheral fat oxidation and glucose transport. Leucine is able to improve peripheral glucose and lipid metabolism independent of appetite and weight regulation, suggesting its potential application in the management of metabolic disorders.

Differential effects of restricted versus unlimited high-fat feeding in rats on fat mass, plasma hormones and brain appetite regulators.

The rapid rise in obesity has been linked to altered food consumption patterns. There is increasing evidence that, in addition to total energy intake, the macronutrient composition of the diet may influence the development of obesity. The present study aimed to examine the impact of high dietary fat content, under both isocaloric and hypercaloric conditions, compared with a low fat diet, on adiposity, glucose and lipid metabolism, and brain appetite regulators in rats. Male Sprague-Dawley rats were exposed to one of three diets: control (14% fat), ad lib high-fat palatable (HFD, 35% fat) or high-fat palatable restricted (HFD-R, matched to the energy intake of control) and were killed in the fasting state 11 weeks later. Body weight was increased by 28% in unrestricted HFD fed rats, with an almost tripling of caloric intake and fat mass (P < 0.001) and double the plasma triglycerides of controls. Glucose intolerance and increased insulin levels were observed. HFD-R animals calorie matched to control had double their fat mass, plasma insulin and triglycerides (P < 0.05). Only ad lib consumption of the HFD increased the hypothalamic mRNA expression of the appetite-regulating peptides, neuropeptide Y and pro-opiomelanocortin. Although restricted consumption of palatable HFD had no significant impact on hypothalamic appetite regulators or body weight, it increased adiposity and circulating triglycerides, suggesting that the proportion of dietary fat, independent of caloric intake, affects fat deposition and the metabolic profile.

Established maternal obesity in the rat reprograms hypothalamic appetite regulators and leptin signaling at birth.

OBJECTIVE: Key appetite regulators and their receptors are already present in the fetal hypothalamus, and may respond to hormones such as leptin. Intrauterine food restriction or hyperglycemia can reprogram these circuits, possibly predisposing individuals to adverse health outcomes in adulthood. Given the global obesity epidemic, maternal overweight and obesity is becoming more prevalent. Earlier, we observed rapid growth of pups from obese dams during the suckling period. However, it is unclear whether this is because of alterations in leptin and hypothalamic appetite regulators at birth. DESIGN: Female Sprague-Dawley rats were fed palatable high-fat diet (HFD) or chow for 5 weeks to induce obesity before mating. The same diet continued during gestation. At day 1, after birth, plasma and hypothalamus were collected from male and female pups. MEASUREMENTS: Body weight and organ mass were recorded. Leptin and insulin levels were measured in the plasma by radioimmunoassay. Hypothalamic mRNA expression of neuropeptide-Y (NPY), pro-opiomelanocortin, leptin receptor and its downstream signal, STAT3 (signal transducer and activator of transcription 3), were measured using real-time PCR. RESULTS: Body and organ weights of pups from obese dams were similar to those from lean dams, across both genders. However, plasma leptin levels were significantly lower in offspring from obese dams (male: 0.53+/-0.13 vs 1.05+/-0.21 ng ml(-1); female: 0.33+/-0.09 vs 2.12+/-0.57 ng ml(-1), respectively; both P<0.05). Hypothalamic mRNA expression of NPY, pro-opiomelanocortin, leptin receptor and STAT3 were also significantly lower in pups from obese dams. CONCLUSION: Long-term maternal obesity, together with lower leptin levels in pups from obese dams may contribute to the lower expression of key appetite regulators on day 1 of life, suggesting altered intrauterine neuron development in response to intrauterine overnutrition, which may contribute to eating disorders later in life.

Leptin reduces food intake but does not alter weight regain following food deprivation in the rat.

OBJECTIVE: When animals are allowed free access to food following an extended period of food restriction, body weight is steadily restored to the pre-food restriction level, ie to a specific body weight 'set-point'. We tested the proposition that leptin is used as a signal by the brain to regulate body weight 'set-point'. To this end, we determined whether long-term leptin infusion in rats would prevent the normal weight regain after food restriction. METHODS: Male Sprague-Dawley rats received leptin (leptin-treated) or saline (vehicle-treated) by intravenous infusion. After a 2 week run-in period, food intake was adjusted to 50% of each individual's normal intake for 12 days. Two days prior to the return of unlimited access to food, one group of animals received continuous leptin infusion at 3 micro g/h for the next 14 days. Blood samples taken from the tail vein were used to determine leptin concentrations. A third group of animals that did not undergo food restriction but received saline infusion served as control. As leptin acts in the brain to modulate neuropeptide Y (NPY) levels, hypothalamic NPY content was measured at the end of the study. RESULTS: Food restriction to 50% normal intake for 12 days induced a 20% weight loss and significant reductions in plasma leptin compared with non-restricted control rats (0.5+/-0.1 vs 2.6+/-0.4 ng/ml, P<0.05). Intravenous infusion of leptin increased leptin concentrations four-fold compared with vehicle-treated animals (9.5+/-1.3 vs 2.2+/-0.4 ng/ml, P<0.05). The infusion of leptin attenuated the increase in daily food intake after free access to food was resumed (P<0.05 at 4, 6 and 8 days). Despite this, both groups of previously restricted rats had regained the same amount of weight after 12 days of ad libitum feeding. No difference was noted in NPY levels measured in the arcuate nucleus and the paraventricular nucleus, in line with the similar amounts of food eaten by all rats at the end of the experiment. CONCLUSION: Increasing plasma leptin concentrations just prior to the end of a period of food restriction reduced subsequent food intake, but did not appear to exert a major influence on the body weight 'set-point', as leptin did not prevent weight regain. The results of the present study suggest that leptin may be of little value in maintaining weight loss in individuals who have lost weight through dieting. Further research is required to understand the role of leptin in the regulation of energy balance.

Involvement of neuropeptide Y in glucose sensing in the dorsal hypothalamus of streptozotocin diabetic rats - in vitro and in vivo studies of transmitter release.

AIMS: Within the brain, subgroups of neurons respond differently to altered glucose concentrations. Identification of neuropeptide Y in hypothalamic neurons that sense glucose suggests a role for neuropeptide Y in glucose sensing. Using in vitro and in vivo techniques to monitor transmitter release, we investigated whether lowering glucose concentration affects the release of neuropeptide Y from the brain, and whether this process is altered in Type I (insulin-dependent) diabetes mellitus. METHODS: Male Sprague-Dawley rats were treated with 48 mg/kg streptozotocin or vehicle intravenously. The effect of reduced glucose on endogenous neuropeptide Y overflow from slices of hypothalamus and medulla incubated in Krebs solution was examined 4 weeks later. The hypothalamus was separated into a dorsal region containing the paraventricular nucleus and a ventral region containing the arcuate nucleus. RESULTS: Streptozotocin-induced diabetes increased basal neuropeptide Y overflow in the dorsal and ventral hypothalamus ( p<0.05) but not the medulla. In vitro neuropeptide Y overflow was reduced by low glucose in the dorsal hypothalamus in diabetic, but not in control rats. No effect of reduced glucose was observed in the ventral hypothalamus or medulla. In vivo push-pull studies in the paraventricular nucleus also showed greater neuropeptide Y overflow in diabetic rats relative to control rats ( p<0.05). Insulin-induced hypoglycaemia induced a decrease in neuropeptide Y overflow in diabetic rats, while an increase was observed in control rats ( p<0.05). CONCLUSION: These region-specific effects of low glucose on neuropeptide Y overflow in diabetic rats support a part for neuropeptide Y in altered glucose sensing in Type I diabetes.

Estrogen deficiency causes central leptin insensitivity and increased hypothalamic neuropeptide Y.

OBJECTIVE: Altered fat distribution is a consequence of menopause, but the mechanisms responsible are unknown. Estrogen insufficiency in humans can be modeled using ovariectomized rats. We have shown that increased adiposity in these rats is due to reduced physical activity and transient hyperphagia, and can be reversed with 17beta-estradiol treatment. The aims of this study were to examine whether this altered energy balance is associated with circulating leptin insufficiency, central leptin insensitivity, decreased hypothalamic leptin receptor (Ob-Rb) expression, and/or increased hypothalamic neuropeptide Y (NPY). METHODS: Plasma leptin levels, adipose tissue ob gene expression, energy balance responses to i.c.v. leptin, hypothalamic Ob-Rb expression and NPY concentration in five separate hypothalamic regions were measured in adult female rats after either ovariectomy or sham operations. RESULTS: Obesity was not associated with hypoleptinemia or decreased ob gene expression in ovariectomized rats; however, it was associated with insensitivity to central leptin administration. Food intake was less suppressed and spontaneous physical activity was less stimulated by leptin. This was not due to decreased hypothalamic Ob-Rb expression. NPY concentration in the paraventricular nucleus of the hypothalamus was elevated in the ovariectomized rats, consistent with leptin insensitivity; however this effect was transient and disappeared as body fat and leptin levels increased further and hyperphagia normalized. CONCLUSION: Impaired central leptin sensitivity and overproduction of NPY may contribute to excess fat accumulation caused by estrogen deficiency.

Effects of vagal and splanchnic section on food intake, weight, serum leptin and hypothalamic neuropeptide Y in rat.

Truncal vagotomy can cause reduced food intake and weight loss in humans and laboratory animals. In order to investigate some of the factors that might contribute to this effect, we studied changes in ingestive behaviour, whole body and organ weights, serum leptin and hypothalamic neuropeptide Y in rats with bilateral vagal section, bilateral splanchnic nerve section and combined vagotomy plus splanchnectomy. Pyloromyotomy was combined with vagotomy to lessen effects of vagotomy on gastric emptying. Animals with vagotomy or vagotomy plus splanchnectomy lost weight and decreased their daily food intake relative to animals with splanchnectomy alone, rats with bilateral sham exposure of one or both nerve, or rats with pyloromyotomy alone. Serum leptin and white fat mass, 4 weeks after vagotomy, were about 20% of the values in the sham-operated animals at this time. No effect for splanchnic nerve section alone was observed. Pyloromyotomy caused no reduction in weight or fat mass, but reduced serum leptin. Following vagotomy with or without splanchnic nerve section, neuropeptide Y was elevated in the arcuate nucleus relative to values for the other four groups. Changes in neuropeptide Y were inversely correlated with levels of serum leptin. It is concluded that the effect of vagotomy could be due to the loss of a feeding signal carried by vagal afferent neurons, or to changed humoral signals, for example, increased production of a satiety hormone. However, it cannot be attributed to signals that reduce feeding (for example, gastric distension) reaching the central nervous system via the splanchnic nerves. The changes were sufficient to cause weight loss even though serum leptin was decreased, a change that would be expected to increase food intake.

Enhanced inhibitory feeding response to alpha-melanocyte stimulating hormone in the diet-induced obese rat.

A dysregulation in the hypothalamic neuropeptide systems involved in the control of appetite has previously been shown in models of diet-induced obesity. In the present study, male Sprague-Dawley rats were rendered obese by a highly palatable cafeteria-style diet over 20 weeks, while control rats had access to standard laboratory chow. Feeding responses to alpha-melanocyte stimulating hormone (alpha-MSH), an anorectic peptide and neuropeptide Y (NPY), a potent orexigenic agent were investigated in diet-induced obese and control animals. In addition, endogenous hypothalamic peptide levels were determined in these animals. Intracerebroventricular injections of either 4 nmol alpha-MSH or saline vehicle were given 10 min prior to the onset of the dark phase. Diet-induced obese rats had significantly enhanced nocturnal inhibitory feeding responses to alpha-MSH (P<0.05). The orexigenic feeding response induced by 1 nmol NPY was similar for both groups. At sacrifice, both alpha-MSH and NPY peptide content were selectively reduced in the paraventricular nucleus (PVN) of these animals (P<0.05). Although diet-induced obesity had no effect on responses to NPY, the significantly greater inhibition of nocturnal feeding by alpha-MSH and reduction in PVN alpha-MSH peptide level, suggests melanocortinergic signalling may be reduced in obesity which may account for the hyperphagia of these animals when presented with a palatable diet.

NPY Y1 receptors exert opposite effects on corticotropin releasing factor and noradrenaline overflow from the rat hypothalamus in vitro.

Neuropeptide Y (NPY), corticotropin releasing factor (CRF) and noradrenaline play important roles in the regulation of a number of endocrine and autonomic functions. NPY is co-localised with noradrenaline in the central nervous system and has been observed to modulate noradrenaline release. Recent morphological and physiological studies also support co-modulatory interactions between NPY and CRF. Earlier in vivo studies in our laboratory showed a potentiation of K(+)-stimulated noradrenaline release following NPY administration, possibly due to an NPY Y1 receptor mechanism. In this study, in vitro superfusion techniques were established to simultaneously monitor the release of endogenous noradrenaline and CRF from the hypothalamus of adult rats and to examine the direct neuromodulatory action of NPY on the overflow of CRF and noradrenaline. Administration of 0.10 microM NPY significantly increased CRF overflow to 395% basal levels and reduced hypothalamic noradrenaline overflow to 61% of basal levels. These effects were blocked by prior administration of the NPY Y1 receptor antagonist GR231118. Thus, this study suggests that NPY, working through a Y1 receptor, has dual and opposing effects on CRF and noradrenaline overflow in vitro.

Reduced BAT function as a mechanism for obesity in the hypophagic, neuropeptide Y deficient monosodium glutamate-treated rat.

Neuropeptide Y (NPY) exerts effects on food intake at the level of the paraventricular nucleus (PVN), which receives a dense projection from the arcuate nucleus. Monosodium glutamate (MSG) has been shown to induce hyperadiposity despite hypophagia associated with chemical ablation of the arcuate nucleus. We investigated the mechanism for the excess fat accumulation by studying the time course of changes in brain NPY content, food intake, leptin levels and BAT GLUT4 content after neonatal MSG treatment. Male rat pups were injected with MSG or saline vehicle on days 2, 4, and 6 and examined at 30 and 90 days. Plasma leptin, body mass, length, adipose tissue mass and brown fat GLUT4 were measured and brains dissected for measurement of NPY content. By 30 days, NPY concentrations were reduced in the arcuate nucleus and anterior hypothalamus, and animals tended to be hypophagic. Peripheral adipose tissue levels were less than controls, in line with their low leptin concentrations. At 90 days, MSG treatment was associated with marked reductions in NPY concentrations in several hypothalamic areas, including the PVN and arcuate nucleus, along with increased adiposity and plasma leptin. Animals also displayed marked hypophagia. Levels of GLUT4 transporter were reduced in brown adipose tissue at both ages. The early decrease in brown fat GLUT4 suggests an impairment of the hypothalamic sympathetic input to brown fat which disrupts thermogenesis, contributing to the development of adiposity in the presence of hypophagia.

Modulation of neuropeptide Y overflow by leptin in the rat hypothalamus, cerebral cortex and medulla.

This study examined whether leptin can exert inhibitory actions on brain NPY overflow in Sprague-Dawley and in lean and obese Zucker rats, and tested the site-specificity of the effect. Slices of rat hypothalamus, cerebral cortex and medulla oblongata were perfused with modified Krebs buffer containing either leptin or KCl. Depolarization of tissues with 40 mM KCl elicited a significant doubling of NPY overflow in all brain regions tested. At 1 microM, leptin significantly reduced NPY overflow only in the rat hypothalamus, while at 3 microM, leptin reduced NPY overflow from all regions. However, no effect of 1 microM leptin was observed in the hypothalamus of obese Zucker rats: this insensitivity to leptin is in keeping with their genetic defect. In conclusion, the inhibitory effect of leptin on hypothalamic NPY overflow provides further evidence for important modulatory actions between these two feeding mediators. Moreover, the effect of leptin observed in the cerebral cortex and medulla oblongata supports a role of leptin in brain regions other than the hypothalamus.

In vitro studies of endogenous noradrenaline and NPY overflow from the rat hypothalamus during maturation and ageing.

Marked changes in brain monoamine content and NPY content occur during maturation and ageing. Earlier in vivo studies in our laboratory have reported blunted K+ stimulated noradrenaline release and reduced NPY overflow in aged animals using microdialysis and push pull techniques. In this study, in vitro superfusion techniques were established to measure endogenous noradrenaline, NPY, DOPAC and 5-HIAA overflow from the hypothalamus of 1, 5 and 16 month old Sprague-Dawley rats. A period of high K+ (56 mM) stimulation was carried out to elicit maximal release. Basal noradrenaline overflow was similar in all age groups of rats and during K+-induced depolarisation similar 3-4 fold increases were observed. On the other hand, basal and K+ stimulated NPY overflow were significantly greater in the adult rats compared to 1 month and 16 month old rats. Despite differences in absolute NPY overflow, the relative increase over resting was not significantly different across age groups. The molar quantities of hypothalamic NPY overflow at rest and under K+ stimulated conditions were three orders of magnitude lower than noradrenaline. Results of these studies suggest that both NPY and noradrenaline can be released from a similar hypothalamic pool. Basal and K+-evoked DOPAC and 5-HIAA overflow were similar between the 3 age groups. Thus the overflow of hypothalamic noradrenaline, DOPAC and 5-HIAA under in vitro conditions was not altered from 1 to 16 months. In contrast, 5 month old rats had significantly higher NPY overflow than the other age groups (P < 0.05), consistent with a reported decline in NPY content with advanced age. Hypothalamic noradrenaline overflow was not affected by ageing, suggesting that a selective loss of NPY in the arcuo-PVN projection, or other projections to the hypothalamus with ageing may contribute to the reduction in NPY overflow in aged rats.

Effects of increasing gestation, cortisol and maternal undernutrition on hypothalamic neuropeptide Y expression in the sheep fetus.

We have characterized the localization and the ontogenetic changes in Neuropeptide tyrosine (NPY) before birth and investigated the regulation of NPY expression by cortisol and undernutrition in the fetal sheep hypothalamus during late gestation. Using immunohistochemistry, we have identified NPY-containing neurons in the infundibular nucleus and the internal layer of the median eminence in fetal hypothalami collected between 110 and 147 days gestation. NPY projections were also present in the paraventricular nucleus (PVN) of fetal hypothalami at all ages between 110 days gestation and term. There was a significant increase in the amount of immunoreactive NPY/g hypothalamus between 87 and 113 days and 131-140 days gestation and a further significant increase after 141 days gestation. The total hypothalamic content of immunoreactive NPY increased significantly between 87 and 113 days and 141-145 days gestation. The levels of NPY mRNA: 18S rRNA in the mediobasal region of the fetal hypothalamus were significantly higher at 145-146 days gestation than at any earlier gestational age between 116 and 141 days gestation. Cortisol (2.5-3.0 mg/24 h) was infused intrafetally between 109 and 116 days gestation. The ratio of NPY mRNA: 18s rRNA in the mediobasal region of the fetal hypothalamus was significantly higher in the cortisol-infused group when compared with the saline-infused control group at 116 days gestation. Maternal, and hence fetal undernutrition, was induced between 110 and 146 days gestation. At 145-146 days gestation the ratio of NPY mRNA: 18S rRNA in the mediobasal region of the fetal hypothalamus was significantly higher in the undernutrition group when compared with control animals. We have therefore demonstrated that NPY is present in the hypothalamus of the sheep fetus before birth and that hypothalamic NPY content and NPY mRNA increase before delivery. We have also found that glucocorticoids and undernutrition stimulate increases in NPY mRNA levels in the hypothalamus before birth.

Central interactions between noradrenaline and neuropeptide Y in the rat: implications for blood pressure control.

Neuropeptide Y (NPY) and noradrenaline are co-localised in central neurones and both transmitters exert cardiovascular effects. Using microdialysis and push-pull techniques to measure transmitter release in vivo, and microinjection studies, we examined the role(s) of central noradrenaline and NPY in blood pressure regulation in the hypothalamus and nucleus tractus solitarius (NTS) of the rat. Hypothalamic noradrenaline release was increased following haemorrhage and reduced after phenylephrine infusion. Ageing is associated with markedly reduced NPY concentrations in the hypothalamus. 18-month old animals showed a reduced ability to release both NPY and noradrenaline to a potassium depolarisation stimulus. NTS administration of NPY induced dose-dependent decreases in blood pressure and heart rate. The depressor but not the bradycardic response was attenuated by prior administration of yohimbine. NTS microinjection of 23 pmol NPY induced similar cardiovascular effects in spontaneously hypertensive and Wistar Kyoto rats. NPY and noradrenaline appear to interact at several sites in the brain known to be important for blood pressure control.

Region-specific neuropeptide Y overflows at rest and during sympathetic activation in humans.

Neuropeptide Y coexists with norepinephrine in sympathetic nerves and is coreleased into the circulation on sympathetic activation. Little is known about the regional release of neuropeptide Y in humans under normal conditions or in pathophysiological situations of sympathetic activation or denervation. We measured plasma neuropeptide Y-like immunoreactivity and norepinephrine concentrations in samples taken from the brachial artery; coronary sinus; and internal jugular, antecubital, or hepatic veins in volunteers aged 20 to 64 years. Regional neuropeptide Y overflow at rest was calculated from venoarterial plasma concentration differences and plasma flow, and norepinephrine spillover was determined by [3H]norepinephrine infusion techniques. Cardiac release of neuropeptide Y and norepinephrine was examined in response to various stressors as well as in clinical models of sympathetic activation, cardiac failure, and denervation after cardiac transplantation. In healthy volunteers, cardiac, forearm, and jugular venous sample neuropeptide Y concentrations were similar to arterial levels. Hepatic vein plasma neuropeptide Y was greater than arterial both at rest (119 +/- 5% of arterial, n = 7) and after a meal (132 +/- 12%, n = 7), with neuropeptide Y overflows of 6 +/- 2 and 11 +/- 2 pmol/min, respectively. In contrast, hepatomesenteric norepinephrine spillover was not significantly increased by feeding. Although coronary sinus plasma norepinephrine concentrations increased significantly with the cardiac sympathetic activation accompanying mental arithmetic, coffee drinking, isotonic exercise, and bicycle exercise, only the latter powerful sympathetic stimulus increased neuropeptide Y overflow. Cardiac failure was associated with increased resting release of both norepinephrine and neuropeptide Y from the heart, whereas postcardiac transplant norepinephrine spillover from the heart was reduced. The net overflow of neuropeptide Y to plasma observed at rest across the hepatic circulation, but not the cardiac, forearm, or cerebral circulations, indicates that the gut, the liver, or both make a major contribution to systemic plasma neuropeptide Y levels in humans. Sympathetic activation by exercise produced a modest increase in cardiac neuropeptide Y overflow but to only approximately 25% of the resting input from the gut and without a change in arterial neuropeptide Y concentration. Plasma neuropeptide Y measurements are less sensitive than those of plasma norepinephrine concentrations as an index for quantifying sympathetic neural responses regulating the systemic circulation.

Embryonic hypothalamic tissue transplanted to the IVth ventricle of newborn Brattleboro rats.

The hypothalamic region, dissected from normal rat embryos, was transplanted into the IVth ventricle of newborn mutant Brattleboro rats. Water intake and urine osmolality were measured in both the recipient animals and unoperated littermate controls during a 7-week period following weaning. No differences were found between operated and unoperated animals. Ten weeks after transplantation, host animals were fixation perfused and the brains prepared for either catecholamine fluorescence or vasopressin immunohistochemistry. Well-developed grafts were found in the IVth ventricle of the hosts. They received innervation from the host locus coeruleus and contained many neurons with vasopressin-like immunoreactivity. Vasopressin-containing fibers were found running from the grafts into the host medulla.

Specific changes in hypothalamic alpha-adrenoceptors in young spontaneously hypertensive rats.

Changes in the activity of hypothalamic and brain-stem adrenergic neurons have been reported in young spontaneously hypertensive rats (SHR) prior to the development of hypertension. We have measured central alpha- and beta-adrenoceptor concentrations in 4-week-old SHR and Wistar-Kyoto (WKY) controls by direct radioligand binding studies using [3H]prazosin (alpha 1), [3H]clonidine (alpha 2), and [125I]iodohydroxybenzlpindolol (beta). The concentration of alpha 2-adrenoceptors was significantly elevated in the hypothalamus of the SHR, 156.9 +/- 10.4 compared with WKY, 119.4 +/- 10.0 fmole/mg protein (n = 7, mean +/- SEM, p less than 0.0125). Alpha 2-adrenoceptor concentrations in both the brain stem and cerebral cortex were similar in the two groups of animals. The increase in hypothalamic adrenoceptors was specific for alpha 2-adrenoceptors, since similar concentrations of alpha 2- and beta-adrenoceptors were found in this region.