Peptides and feeding

Poor Appetite in Frail Older Persons-A Systematic Review

Anorexia of aging is a common problem in older adults. Depending on the setting, its prevalence varies from about 10% (among community-dwelling older adults) to over 30% in acute wards and nursing homes. The objective of this systematic review was to establish the prevalence of poor appetite in frail persons ≥60 years of age. We performed a literature search for studies where the prevalence of anorexia of aging among frail and pre-frail old adults was reported. 957 articles on this topic were identified. After eligibility assessment, three articles were included in the review. The studies included 4657 community-dwelling older adults. The weighted total prevalence of anorexia of aging in all the included studies was 11.3%. Among frail and pre-frail participants, loss of appetite was reported in 20.5% (weighted estimate). Overall, robust status was associated with a 63% lower probability of concomitant anorexia of ageing (OR 0.37, 95%CI 0.21-0.65, p = 0.0005). Frailty or risk of frailty are associated with more prevalent anorexia of ageing. This has potential practical implications; however, more research, especially to elucidate the direction of the relation, is needed.

Influence of Griffonia simplicifolia on male sexual behavior in rats: behavioral and neurochemical study

The seeds of Griffonia simplicifolia Baill. are rich in 5-HTP (5-hydroxytryptophan), a direct precursor of the neurotransmitter serotonin. In the present study we investigated the influence of the plant extract on male sexual behavior. The seed extract was orally administered to Sprague-Dawley male rats at three dose levels (25, 50 and 100 mg/kg) both acutely and subchronically (daily for 9 days). Mating test with receptive female rats was performed 60 min after the acute treatment or the last dose when repetitively administered. Mount, intromission and ejaculation latencies and post-ejaculatory interval were recorded. Food intake and body weight were measured over the 9-day period of treatment. Microdialysis technique was used to detect the extracellular levels of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in rat brain following the acute administration of the extract dosed at 100mg/kg. The acute treatment significantly increased mount latency (at any dosage), intromission and ejaculation latencies (at 100 mg/kg) and post-ejaculatory interval (at 50 and 100 mg/kg). On the contrary the subchronic treatment failed to exert a significant influence on copulatory behavior. The daily administration of the extract dosed at 50 and 100 mg/kg for 9 days significantly reduced food intake and body weight. Finally in the microdialysis experiments we found a dramatic increase in 5-HT and its metabolite 5-HIAA.

The effects of testosterone manipulation on the body condition of captive male yellow-legged gulls

Persistently high testosterone levels are believed to be costly to males due to their negative effect on body condition. However, this assumption could not be validated when we analysed birds isolated from all social interactions. The hypothesis was tested on birds kept in isolation in order to analyse the effects of testosterone per se, and thereby exclude the influence of social interactions. Adult male yellow-legged gulls (Larus cachinnans) were captured, and after a period of adjustment, some individuals were subcutaneously implanted with testosterone, while the rest were used as controls. The gulls received ad libitum food for 10 days and were then fasted for 4 days. Thyroid hormones, body-mass change, daily food intake, hematocrit and several plasma biochemical parameters were analysed. Treated (T)-males maintained constant levels of plasma total protein throughout the experiment, whilst control (C)-males showed a decrease. We did not find any other differences between groups for the other variables analysed. Since the implanted birds sustained high testosterone levels for a number of days, any cost to body condition would have been revealed if these costs levels were actually important. Our results do not support the hypothesis that a reduction in body condition can be directly produced by plasma testosterone, although total protein changes do suggest different anabolic patterns in testosterone-treated gulls.

Aetiopathogenesis and pathophysiology of bulimia nervosa: biological bases and implications for treatment

Bulimia nervosa is an eating disorder characterised by recurrent episodes of binge eating and associated efforts to purge the ingested calories through self-induced vomiting, laxative or diuretic abuse, fasting or intensive exercise. The aetiopathogenesis and pathophysiology of the disorder are currently unclear. Biological bases have been proposed repeatedly, based on several lines of evidence: hunger, satiety and food choice are regulated by neurotransmitters and neuropeptides, and impairment of eating habits may be related to alterations in the secretion of these chemicals; genetic studies suggest that these neurotransmitter systems are dysfunctional in individuals with bulimia nervosa; and the frequent comorbidity of bulimia nervosa with major depressive and obsessive-compulsive disorders, conditions in which multiple alterations of brain biochemical functions have been demonstrated. Data in the literature suggest that levels of noradrenaline (norepinephrine) and serotonin (5-hydroxytryptamine; 5-HT) are lower in individuals with bulimia nervosa than in healthy controls. Levels of dopamine are similar to, or lower than, those in controls. After remission of the disorder, noradrenergic function returns to that seen in controls, whereas dopaminergic and serotonergic function rebound to levels higher than in controls. Among the neuropeptides, alterations in the levels of neuropeptide Y, peptide YY, beta-endorphin, corticotrophin-releasing hormone, somatostatin, cholecystokinin and vasopressin have been found in the symptomatic phase of bulimia nervosa, with a return to levels seen in controls after remission. Pharmacological treatment of bulimia nervosa that is directed at correction of the neurochemical alterations observed is difficult because of the complexity of the impairments. However, such treatment is necessary and should be continued long after symptomatic remission to ensure reinstitution of cerebral biochemical homeostasis.

Effects of peptides on animal and human behavior: a review of studies published in the first twenty years of the journal Peptides

This review catalogs effects of peptides on various aspects of animal and human behavior as published in the journal Peptides in its first twenty years. Topics covered include: activity levels, addiction behavior, ingestive behaviors, learning and memory-based behaviors, nociceptive behaviors, social and sexual behavior, and stereotyped and other behaviors. There are separate tables for these behaviors and a short introduction for each section.

Effects of small-intestinal fat and carbohydrate infusions on appetite and food intake in obese and nonobese men

To determine whether the satiating effects of nutrients in the small intestine are lower in obese than in nonobese people, 9 healthy, obese men [age: 18-33 y; body mass index (BMI; in kg/m2) 30.4-40.8] and 11 healthy, nonobese men (age: 18-33 y; BMI: 19.1-26.4) received an intraduodenal infusion of saline (control), lipid ( 11.97 kJ/min, or 2.86 kcal/min), or glucose (11.97 kJ/min) for 120 min on separate days. Fullness, hunger, and nausea were assessed by visual analogue scales. After the infusions, a meal was offered and food intake was quantified. There was no difference in appetite ratings between the obese and nonobese subjects during the infusions, in the amount or macronutrient composition of food eaten after the infusions, or in the time taken to eat the meals. Both the lipid and glucose infusions were associated with greater fullness than the control infusion. The energy content of the food eaten was less after the lipid infusion than after either the control or glucose infusion (P < 0.01): lipid infusion suppressed energy intake by 22% compared with the control infusion and by 15% compared with the glucose infusion. Suppression of energy intake after intraduodenal nutrient infusions was due to slower eating (P < 0.01). Intraduodenal infusions of fat suppressed appetite and food intake more than did equienergetic infusions of carbohydrate in both obese and nonobese young men, and the responses to intraduodenal fat and glucose were not affected by obesity. The latter observation suggests that established obesity is not associated with reduced small-intestinal responses to dietary fat or carbohydrate.

Effect of glucose supplementation on appetite and the pyloric motor response to intraduodenal glucose and lipid

The effects of different macronutrients on appetite and pyloric motility and the impact of short-term dietary glucose supplementation on these responses were evaluated. Ten males (aged 19-38 yr) received isocaloric (2.9 kcal/min) intraduodenal infusions of glucose and lipid while antropyloroduodenal motility and appetite were assessed by manometry and visual analog scales, respectively. Effects of each intraduodenal nutrient on appetite and motility were evaluated before and after 7 days of dietary supplementation with glucose (400 g daily). Initially, both nutrients caused a similar rise in pyloric tone, but intraduodenal lipid was a more potent stimulus of phasic pyloric motility (P = 0.05) and suppressed appetite more (P = 0.013) than intraduodenal glucose. After dietary glucose supplementation, the increase in pyloric tone during intraduodenal glucose was attenuated. Although intraduodenal lipid remained a more potent stimulant of phasic pyloric motility (P = 0.016), it no longer decreased appetite. We conclude that in healthy young males 1) intraduodenal infusion of lipid is a more potent stimulus of phasic pyloric motility and suppresses appetite more than intraduodenal glucose and 2) dietary glucose supplementation alters both the appetite suppressant effect of intraduodenal lipid and the pyloric motor response to intraduodenal glucose infusion.

Extracellular serotonin in the lateral hypothalamic area is increased during the postejaculatory interval and impairs copulation in male rats

Serotonin (5-HT) is generally inhibitory to masculine sexual behavior. It has been suggested that 5-HT released after ejaculation may promote the sexual quiescence of the postejaculatory interval (PEI). The following experiments were conducted to test (1) whether extracellular 5-HT increases in either the anterior lateral hypothalamic area (LHAA) or the medial preoptic area (MPOA) of male rats after ejaculation; (2) whether increasing 5-HT in these sites, by microinjecting the selective serotonin reuptake inhibitor alaproclate, could inhibit copulatory abilities; and (3) whether copulation deficits produced by alaproclate were attributable to locomotor impairments. The effects of local application of alaproclate on extracellular 5-HT levels in the LHAA and the MPOA were also tested. Extracellular serotonin was measured in all experiments using in vivo microdialysis. Ejaculation was correlated with enhanced 5-HT release from the LHAA; no 5-HT increases were observed before ejaculation, and levels were decreased toward basal values during a subsequent copulatory series. Elevating 5-HT in the LHAA by microinjecting alaproclate inhibited copulation by increasing the latency to mount, intromit, and ejaculate. This inhibition did not result from nonspecific locomotor impairments. In the MPOA, 5-HT release remained stable throughout copulation, and microinjecting alaproclate into this site did not significantly alter sexual behavior. These data support the large body of evidence suggesting that 5-HT is inhibitory to masculine sexual behavior. Furthermore, the LHAA, but not the MPOA, may be one site responsible for serotonergic inhibition of copulation during the PEI.

Reaction of sensorimotor cortex neurons to stimulation of the lateral hypothalamus in conditions of microiontophoretic application of tetragastrin and bradykinin: the role of food reinforcement

Experimental data were obtained on the nature of rabbit sensorimotor cortex neuron reactions to stimulation of the food motivation center of the lateral hypothalamus in conditions in which food was or was not presented to the animals combined with microiontophoretic application of tetragastrin and bradykinin. These neuropeptides were able to alter the relationship between motivation and reinforcement.

The lateral hypothalamic area revisited: ingestive behavior

This article discusses the role of the lateral hypothalamic area (LHA) in feeding and drinking and draws on data obtained from lesion and stimulation studies and neurochemical and electrophysiological manipulations of the area. The LHA is involved in catecholaminergic and serotonergic feeding systems and plays a role in circadian feeding, sex differences in feeding and spontaneous activity. This article discusses the LHA regarding dietary self-selection, responses to high-protein diets, amino acid imbalances, liquid and cafeteria diets, placentophagia, "stress eating," finickiness, diet texture, consistency and taste, aversion learning, olfaction and the effects of post-operative period manipulations by hormonal and other means. Glucose-sensitive neurons have been identified in the LHA and their manipulation by insulin and 2-deoxy-D-glucose is discussed. The effects on feeding of numerous transmitters, hormones and appetite depressants are described, as is the role of the LHA in salivation, lacrimation, gastric motility and secretion, and sensorimotor deficits. The LHA is also illuminated as regards temperature and feeding, circumventricular organs and thirst and electrolyte dynamics. A discussion of its role in the ischymetric hypothesis as an integrative Gestalt concept concludes the review.

Effects of opioid antagonists naloxone and naltrexone on neuropeptide Y-induced feeding and brown fat thermogenesis in the rat. Neural site of action

Neuropeptide Y administered intracerebroventricularly and into the paraventricular nucleus of the hypothalamus stimulates feeding and decreases brown adipose tissue thermogenesis. Although specific neuropeptide Y antagonists are not yet available, previous studies had shown that the opioid antagonist naloxone blocked neuropeptide Y-induced feeding when both drugs were injected intracerebroventricularly. We wanted to find out if naloxone injected into specific brain sites would block neuropeptide Y effects on feeding and brown fat thermogenesis. Rats were double injected in specific brain sites with neuropeptide Y and either naloxone or naltrexone (a congener of naloxone). Food intake and brown fat measures were assessed. Naloxone or naltrexone in the paraventricular nucleus weakly decreased paraventricular nucleus neuropeptide Y-induced feeding and did not affect neuropeptide Y-induced reductions in brown fat activity. Peripheral naloxone blocked intracerebroventricular neuropeptide Y-induced feeding and brown fat alterations. Fourth ventricular naloxone decreased paraventricular nucleus neuropeptide Y-induced feeding, and naltrexone given into the nucleus of the solitary tract blocked paraventricular nucleus neuropeptide Y-induced alterations in feeding and brown fat. These data indicate that neuropeptide Y in the paraventricular nucleus may act on feeding and brown fat thermogenesis through opioidergic pathways in the nucleus of the solitary tract.

Naloxone's effects on operant responding depend upon level of deprivation

Naloxone's effects on initiation, maintenance, and maximal response effort to acquire food were examined in rats maintained under different levels of food deprivation. In Experiment 1, naloxone was administered SC to rats responding under an FR 80 (first pellet) FR 3 (subsequent pellets) reinforcement schedule. Naloxone did not increase time to acquire the first pellet. Naloxone's suppression of subsequent intake and lowest effective dose were inversely related to level of deprivation. In Experiment 2, rats responded for food under a Progressive Ratio 2 reinforcement schedule. Breakpoint was lowered only when rats were maintained with free access to food. Decreases in response and running rate were inversely related to deprivation level. Results are consistent with the hypothesis that opioids are involved in the maintenance but not the initiation of feeding.

Exogenous cholecystokinin octapeptide in broiler chickens: satiety, conditioned colour aversion, and vagal mediation

Intraperitoneal injections of 3.5, 7.0, 14.0, and 28.0 micrograms/kg of CCK-8 into free-feeding broiler chickens significantly reduced food intake and delayed feeding (p < 0.05). To determine whether CCK can condition preference or aversion and to investigate the latency and the reversal of the effect, a low (2 micrograms/kg) and a high (14 micrograms/kg) dose of CCK-8 were administered using the coloured food paradigm. One colour, the conditioning stimulus (CS+), was paired with injections of CCK-8; the other colour was paired with injections of saline (CS-). The 2 micrograms/kg dose of CCK-8 neither reduced food intake nor conditioned a colour aversion. The 14 micrograms/kg dose significantly reduced food intake and conditioned a colour aversion (p < 0.05). When vagotomy was performed, the 14 micrograms/kg dose of CCK suppressed feeding in sham-operated birds (p < 0.05) but not in vagotomized birds (p > 0.05). A significant aversion for the food paired with CCK was obtained in sham-operated birds (p < 0.001) but not in vagotomized birds (p > 0.05). It was concluded that IP injections of CCK-8 reduce food intake in broiler chickens and that chicks can learn to associate the colour of the food with injections of CCK, developing an aversion. It was also shown that the vagus nerve mediates the CCK satiety effects and that aversion conditioning to CCK is dependent upon intact vagal innervation of the viscera.

Peripheral opioid secretory pattern in anorexia nervosa

The peripheral secretion of endogenous opioids was studied in 10 women with restrictive anorexia nervosa and 10 age- and sex-matched healthy controls. The circadian rhythm of beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH), and their responses to the administration of corticotropin releasing hormone (CRH, 1 micrograms/kg body weight, i.v.), clonidine (150 microgram, i.v.), domperidone (10 mg, i.v.), and 5-hydroxytryptophan (5-HTP, 200 mg, p.o.) were examined in patients and controls. The results revealed increased nocturnal secretion of beta-EP and diurnal-nocturnal secretion of beta-LPH with loss of circadian rhythmicity of both peptides, normal response to CRH stimulation, blunted response to clonidine and domperidine, and normal beta-EP and blunted beta-LPH response to 5-HTP stimulation. The data suggest a complex alteration of peripheral opioids and of central aminergic mechanisms that regulate proopiomelanocortin-derived peptide secretion and eating behavior.

Enhancement of finger blood flow response of postprandial human subjects to the increase in body temperature during exercise

The present study was performed to investigate the effect of food intake on thermoregulatory vasodilatation in seven healthy male volunteers. The changes in oesophageal (Toes) and mean skin temperatures, finger and forearm blood flows (BF), oxygen consumption (VO2) and heart rate (fc) with and without food intake were measured before and during a 40-min exercise at an intensity of 35% maximal O2 consumption at an ambient temperature of 25 degrees C. Exercise commenced 60 min after food intake. Ingestion of food equivalent to 50.2 kJ.kg body mass-1 elevated mean body temperature, BF, VO2 and fc in 60 min. Four subjects responded to exercise with a marked increase in finger BF and with no sweating (non-sweating group), while the other three responded with perspiration over almost the whole skin area and with little change in finger BF. Further analyses were made mainly in the non-sweating group. The postprandial increases in Toes, BF, VO2 and fc were persistent during exercise. The rate of increase in finger BF with the increase in Toes and mean body temperature was significantly greater with food intake than without. However, there was no difference in the response of forearm BF to exercise between the two conditions. These results suggested that food intake enhanced finger BF response to the increase in deep body temperature during exercise. It was also concluded that there was a regional difference in cutaneous vasomotor response to thermal load in the postprandial subjects.

CCK as a central satiety factor: behavioral and electrophysiological evidence

CCK and its derivatives potently inhibit feeding, even after vagotomy. This effect is thus considered to be peripheral. Recently, however, the vagal gastric branch was reported to essentially bring feeding inhibition into full play. In the present study, it was found that CCK-8, administered into the third cerebroventricle (III-cv), or into the lateral hypothalamus (LHA), significantly and dose-dependently inhibited feeding induced by electrical stimulation of the contralateral LHA (LHA-ESIF) in the chronic rat. This inhibition by CCK-8 was not affected by systemic pretreatment with proglumide (1 mg), a selective antagonist, while CCK (250 ng) simultaneously microinjected into the III-cv with 5 micrograms proglumide almost completely eliminated the CCK effect on LHA-ESIF. Neuronal activity of the ventromedial hypothalamus (VMH) was enhanced, and that of the LHA was suppressed by electrophoretic direct application of CCK on neurons in urethane-chloralose-anesthetized rats. CCK also markedly decreased the threshold of VMH glucose responding neurons. These results indicate that the satiety effect is not only peripheral, but might also be central, especially through feeding-related hypothalamic neurons, which are probably important in feeding inhibition.

Increase by naloxone of arginine vasopressin and oxytocin responses to insulin-induced hypoglycemia in obese men

The present study was carried out to establish whether the low arginine vasopressin (AVP) and oxytocin (OT) responses to insulin-induced hypoglycemia observed in obese men was due to alteration of the opioid control of posterior pituitary function. For this purpose, the AVP and OT releasing effect of insulin (0.15 IU/kg bw)--induced hypoglycemia was tested in eight normal weight men and in 10 age-matched obese subjects, without and with the previous treatment with the specific opioid receptor antagonist naloxone (3 mg in an iv bolus). In a control study, naloxone was given alone to the same subjects. Obese men showed similar basal glucose, AVP and OT levels, which remained unmodified after treatment with naloxone alone. Insulin induced a similar decrement of blood glucose levels in all subjects, with a nadir at 30 min. Plasma levels of AVP and OT rose strikingly in normal and obese subjects with mean peak responses at 30 min for AVP and at 45 min for OT. However, both AVP and OT responses were significantly lower in obese than in control subjects. Pretreatment with naloxone did not modify the AVP and OT responses to hypoglycemia in normal weight subjects, whereas it significantly enhanced both hormonal responses in obese subjects. In the presence of naloxone normal controls and obese subjects showed similar responses of both AVP and OT to hypoglycemia. These data indicate that an abnormal activity of endogenous opioids might account for the hypothalamic posterior pituitary dysfunction, which is responsible for the low AVP and OT responses to insulin-induced hypoglycemia in obesity.

Neuroendocrine mechanisms involved in regulation of body weight, food intake and metabolism

Body weight regulation is the result of food intake and energy expenditure. The central nervous system (CNS), and in particular, the hypothalamus, controls food intake as well as metabolism, the latter mainly by autonomic effects on the islet of Langerhans, hepatocytes and adipocytes. Body weight, more precisely body fat content, is probably controlled by a feedback mechanism in which insulin, released from the B cell of the islet of Langerhans, plays a key role. The islet of Langerhans is an intricate neuroendocrine unit in which the release of glucagon, insulin, and somatostatin from A, B, and D cells, respectively, is controlled by the CNS via a rich autonomic innervation. In addition, the endocrine cells of the pancreas influence each other by paracrine actions. The CNS control of the islets shapes the plasma insulin and blood glucose profiles during the circadian cycle and thereby regulates the nutrient flow to the different tissues in the body. Thus, the CNS structures involved in regulation of body weight and food intake control also metabolism. The mechanisms contributing to match food intake and the needs of metabolism are discussed.

Luteinizing hormone and cortisol responses to naloxone in normal weight women with bulimia

The present study was undertaken in order to establish whether alterations in the endogenous opioid control of luteinizing hormone (LH) and ACTH/cortisol secretion occur in bulimic women with normal body weight and normal menstrual cycles. For this purpose, the capability of the opioid antagonist naloxone (4 mg injected as an intravenous bolus at time 0, plus 10 mg infused over 2 hr) to increase the circulating levels of LH and cortisol was tested in nine bulimic women and in nine age- and weight-matched normal controls. All women were tested on the 22nd day of a normal menstrual cycle. Two days later, a control test with normal saline (NaCl 0.9%) instead of naloxone was performed. The basal levels of LH and cortisol were similar in the bulimic and normal subjects and were not modified by the administration of normal saline. In contrast, the administration of naloxone significantly increased plasma LH and cortisol levels in all subjects, with peak LH responses at 30 min and peak cortisol responses at 60 min. The naloxone-induced LH and cortisol increases were significantly higher in the bulimic women than in the normal controls. These data indicate the presence of an increased opioid inhibitory tone in the control of LH and ACTH/cortisol secretion in normal weight bulimic women with normal menstrual cycles.

Intracranial microinfusion of pancreastatin elevates blood glucose, free fatty acids, and corticosterone in rats

Pancreastatin, a novel peptide recently isolated from porcine pancreas, significantly inhibits insulin and somatostatin release and augments glucagon release from the isolated perfused rat pancreas. This implies a role for endogenous pancreatic pancreastatin in the regulation of blood glucose and free fatty acids, the two major metabolic fuels. Since many peptides have similar biological effects when administered centrally and peripherally, the effects of centrally administered pancreastatin on blood glucose and free fatty acids were examined in 3 studies. Corticosterone was also measured in two of these studies. Intraventricular microinfusion of pancreastatin significantly elevated blood glucose, free fatty acid, and corticosterone concentrations in a dose-related manner. None of these effects was seen after subcutaneous injection of the same doses. Centrally administered pancreastatin appears to produce its effects on glucose and free fatty acids through actions in the brain, and either the brain, the median eminence, and/or pituitary for corticosterone.

Effects of nocturnal intraperitoneal administration of cholecystokinin in rats: simultaneous increase in sleep, increase in EEG slow-wave activity, reduction of motor activity, suppression of eating, and decrease in brain temperature

Rats received an i.p. injection of cholecystokinin-octapeptide sulfate ester (CCK; 4, 10 or 50 micrograms/kg) or physiological saline at dark onset, and the 24-h sleep-wake cycle (12-h-dark and 12-h-light phases), spontaneous motor activity and brain temperature (Tbr) were recorded. EEG activity was studied through spectral analysis for 2.5 h, and food intake was measured at the end of postinjection hour 1. In response to CCK, non-REM sleep increased at the expense of wakefulness, and the sleep-promoting effect was substantiated by an increase in EEG slow-wave activity. Motor activity, Tbr and food intake decreased. The effects vanished in postinjection hour 2; the diurnal rhythms were not modified. The changes varied as a function of the dose: the effects were significant following 10 micrograms/kg, and even higher in response to 50 micrograms/kg CCK. The results indicate that i.p. CCK definitely promotes non-REM sleep. This effect may belong to the behavioral sequence elicited by the peptide, which is often attributed to satiety. As evidenced by the reduction of Tbr, CCK also exerts strong autonomic actions, which might interfere with the behavioral responses.

Anorexia in the elderly

Weight loss and anorexia occur commonly in the elderly. While in many cases the anorexia can be attributed to associated disease processes, it does appear that a true anorexia of aging exists. Animal studies have suggested that older rodents have an excessive satiety effect of cholecystokinin and a decreased opioid feeding drive. Other older persons develop anorexia in association with depression. In these subjects, excess corticotropin-releasing factor may be the neurotransmitter involved in the pathogenesis of the anorexia. In Alzheimer's disease, decreases in norepinephrine and neuropeptide Y may be involved in the anorexia seen in the these patients.

Hypothalamic food intake regulating areas are involved in the homeostasis of blood glucose and plasma FFA levels

The hypothalamus fulfills multiple functions, e.g., integration of food and water ingestion, various forms of social behavior and physiological neuroendocrine activities. Hypothalamic areas, particularly the ventromedial, lateral and paraventricular areas (VMH, LHA and PVN respectively), that contribute to the regulation of food intake are also involved in the regulation of blood glucose and plasma free fatty acid (FFA) levels. This regulation is controlled both directly via neural pathways and indirectly by hormones, e.g., insulin, glucagon, norepinephrine (NE) and epinephrine (E). A description is presented of the intrahypothalamic connections and the pathways between the hypothalamus and the motor areas of both the sympathetic system in the spinal cord (the intermediolateral column IML) and the parasympathetic system in the brainstem (the dorsal motornucleus of the vagus and the nucleus ambiguus). Noradrenergic stimulation of the LHA, VMH and PVN can alter blood glucose, plasma FFA and insulin levels independently of each other, e.g., noradrenergic stimulation of the VMH leads to an increase of insulin, glucose and FFA. Exercise induced increases of glucose are suppressed by alpha-adrenergic blockade of the LHA, VMH and PVN. Alpha-adrenergic blockade of the VMH during exercise causes an exaggerated increase of plasma FFA whereas alpha-blockade of both the LHA and PVN does not change the normal exercise induced increase of plasma FFA. The apparent contradiction that both adrenergic stimulation and adrenergic blockade of the VMH result in an increase in FFA may be explained by assuming postsynaptic alpha- and beta-adrenergic receptors in the VMH controlling glucose and FFA release respectively and FFA release and presynaptic inhibitory alpha-adrenergic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

An investigation of tolerance to the actions of leptogenic and anorexigenic drugs in mice

This study compared the effects of chronic administration of anorexigenic drugs on weight loss in mice. Tolerance to the effects of peripheral anorexigenic peptides, viz. cholecystokinin-octapeptide and bombesin, developed rapidly. Morphine, cocaine and dehydroepiandrosterone-sulfate caused weight loss and appeared similar to d-amphetamine in mechanisms of action. A high dose of fluoxetine (25 mg/kg) proved to be a potent leptogenic agent but was also associated with death in some animals. A lower dose of fluoxetine (5 mg/kg) was associated with the development of tolerance. Calcitonin, a potent anorexigenic agent, did not produce weight loss and tolerance to its anorectic effect had developed by 10 days. Animals varied widely in their individual responsiveness to a given drug. Peripheral administration of peptide YY caused weight loss. We conclude that acute or chronic effects of agents on food intake do not necessarily predict effects on body weight. However, neurotransmitters that enhance feeding centrally appear to cause weight loss when administered peripherally.

The effects of adrenergic, opioid and pancreatic polypeptidergic compounds on feeding and other behaviors in neonatal leghorn chicks

The present study examined the effects of intracerebral (IC) administration of pancreatic polypeptide (PP), neuropeptide Y (NPY), norepinephrine (NE), dynorphin and naloxone on food intake in 2-day-old Leghorn chicks. Of the compounds studied, only PP (20 micrograms) and naloxone (10 and 20 micrograms) elevated food intake significantly as compared to saline injections. NPY, a potent orexigenic agent in mammals, did not elevate consumption significantly in a dose-related fashion. This latter finding was attributed to the occurrence of tonic-clonic convulsions following NPY administration. However, for those chicks which did not exhibit behavioral convulsions, food intake appeared to be elevated by 1, 5 and 10 micrograms of NPY. Similarly, NE did not elevate food intake but instead induced sedation and narcolepsy, a behavioral response which could be distinguished from the convulsions observed after NPY. In a separate group of chicks, the effect of NPY on cortical activity was examined. Bipolar electrodes were used to record EEG activity before and after IC injections of saline, NPY or NE. The behavioral convulsions induced by NPY corresponded with an increase in high amplitude sharp-wave activity, which persisted for up to 30 min post-injection. Collectively, these results suggest that the neurochemical substrates for feeding in 2-day-old Leghorn chicks are distinct from those underlying food intake in adult mammals.

Immobilisation stress-induced anorexia is not due to gastric ulceration

The relationship between the anorexia following immobilisation and the associated gastric pathology in male and female rats was investigated. Male rats were injected with saline or the histamine-H2. antagonist, ranitidine, which inhibits gastric acid secretion but does not readily enter the brain. Thirty minutes later, the animals were immobilised for 2 hours. Ranitidine pretreatment reduced the number of gastric lesions but had no effect on the degree of stress-induced anorexia. The number of gastric lesions did not correlate significantly with the degree of anorexia or weight loss. Previous studies have reported that female rats (unlike males) exhibit anorexia after repeated daily immobilisations and have greater gastric pathology following stress. Therefore, in a second experiment, female rats were pretreated with saline or ranitidine and immobilised for 2 hours/day for 4 days. The drug did not decrease the number of lesions observed after this treatment. However, as in the first experiment, the number of lesions did not correlate significantly with anorexia or weight loss. It is therefore unlikely that immobilisation stress-induced anorexia in either male or female rats is merely a consequence of gastric ulceration.

Endogenous opiates: 1985

This paper is the eighth installment of our annual review of research involving the endogenous opiate peptides. It is restricted to the non-analgesic and behavioral studies of the opiate peptides published in 1985. The specific topics this year include stress, tolerance and dependence, eating, drinking and alcohol consumption, gastrointestinal and renal activity, mental illness, learning and memory, cardiovascular responses, respiration and thermoregulation, seizures and neurological disorders, activity, and some other selected topics.

Central nervous system effects of peptides, 1980-1985: a cross-listing of peptides and their central actions from the first six years of the journal Peptides

A tabular synopsis is presented for articles concerned with the effects of peptides on the central nervous system that appeared in the journal Peptides from 1980-1985. A table arranged alphabetically by peptide and one arranged by effects, both listing routes of injection, species, direction of change, and qualifying notes, provides easy cross-referencing of peptides and their effects. Over 80 peptides and over 135 effects are listed. The list of peptides includes, but is not limited to: ACTH, angiotensin, bombesin, bradykinin, calcitonin, casomorphin, CCK, ceruletide, CGRP, CRF, dermorphin, DSIP, dynorphin, endorphins, enkephalins, GRF, gastrin, LHRH, litorin, metkephamid, MIF-l, motilin, MSH, NPY, NT, oxytocin, ranatensin, sauvagine, substances P and K, somatostatin, TRH, VIP, vasopressin, and vasotocin. The list of effects includes, but is not limited to: aggression, alcohol, analgesia, attention, avoidance, behavior, cardiovascular regulation, catalepsy, conditioned behavior, convulsions, dopamine binding and metabolism, discrimination, drinking, EEG, exploration, feeding, fever, gastric secretion, GI motility, grooming, learning, locomotor behavior, mating, memory, neuronal activity, open field, operant behavior, rearing, respiration, satiety, scratching, seizure, sleep, stereotypy, temperature, thermoregulation and tolerance.