The effects of proglumide on cholecystokinin-, bombesin-, and glucagon-induced satiety in the rat

Intraperitoneal (IP) administration of the glutaramic acid derivative proglumide inhibited satiety induced by all IP doses of cholecystokinin octapeptide (CCK-OP) in 3-hour food-deprived intact rats. Proglumide did not influence satiety when administered alone and did not inhibit satiety induced by IP glucagon. While proglumide did not inhibit satiety induced by low doses of IP bombesin, it partially and significantly inhibited the satiety effects produced by high doses of this peptide. Since bombesin is a known secretagogue for CCK in several species, these results indicate that while bombesin and CCK act independently to induce satiety, the effect induced by high doses of bombesin is mediated, in part, by the release of endogenous CCK or a structurally related peptide. Furthermore, these results illustrate that proglumide is a specific antagonist of CCK-induced satiety and is, therefore, a potentially useful tool for investigating the physiologic role of this peptide in the control of food intake.     

Nucleus tractus solitarius lesions block the behavioral actions of cholecystokinin

Cholecystokinin (CCK) has been implicated as a signal for the syndrome of satiety in a variety of species. Several lines of evidence point to a peripheral site of action for the behavioral effects of CCK. Peripheral CCK receptors appear to activate a gut-brain pathway involving the sensory fibers of the vagus nerve. To investigate the central anatomical substrate of this visceral-behavioral control system, the terminal regions of the sensory tract of the vagus were lesioned. Radiofrequency lesions of the nucleus tractus solitarius abolished the effects of acute doses of CCK on exploratory behaviors. Sham lesions had no effect on baseline exploratory behaviors and did not influence the ability of CCK to decrease spontaneous exploratory behaviors. These findings delineate the first central site along the ascending sensory pathway which appears to mediate the satiety-related behavioral effects of CCK.     

Paraventricular nucleus lesions abolish the inhibition of feeding induced by systemic cholecystokinin

Peripherally administered cholecystokinin (CCK) initiates a behavioral syndrome which includes reduced food consumption and reduced exploratory behaviors. Previous studies suggest that CCK stimulates receptors in the gut, activating the vagus nerve, which relays sensory information to the nucleus tractus solitarius (NTS) and its ascending pathways. Terminal regions of ascending NTS projections include the paraventricular nucleus of the hypothalamus (PVN), the central nucleus of the amygdala (CNA), and the bed nucleus of the stria terminalis (BNST). Lesions of these three target sites were performed in rats to test the hypothesis that structures postsynaptic to the NTS mediate the behavioral syndrome induced by CCK. Knife cut lesions of the PVN abolished the reductions in feeding induced by CCK (5 and 10 micrograms/kg IP), as compared to sham lesioned control rats. PVN lesions only partially attenuated the reductions in exploration induced by CCK (2.5, 5, and 10 micrograms/kg IP), as compared to sham lesioned control rats. Electrolytic lesions of the CNA partially attenuated the reductions in exploratory behavior induced by CCK (2.5, 5, and 10 micrograms/kg IP), and had no effect on the reductions in feeding induced by CCK (5 and 10 micrograms/kg IP). Electrolytic lesions of the BNST had no effect on either the reductions in feeding or the reductions in exploration induced by CCK. The PVN appears to be one critical forebrain target site for mediating the actions of CCK on feeding. The CNA appears to facilitate the actions of CCK on exploration. Individual components of the behavioral syndrome induced by CCK may be mediated by anatomically distinct forebrain loci.     

The role of central and peripheral cholecystokinin in mediating appetitive behaviors

Cholecystokinin (CCK) reduces total food consumption in mice, rats, pigs, sheep, monkeys and humans. Behaviors associated with an underlying state of satiety are reported after CCK administration. Reductions in exploration and social interactions by CCK are not due to true sedation or sleep, as measured by cortical EEG recordings. The satiety effects appear to be mediated by peripheral CCK receptors, through a feedback loop involving the vagus nerve. The conceptual link between the behavioral functions of CCK as a putative satiety signal and its established digestive functions are discussed.     

Potency of CR 1409, a new proglumide analog, on cholecystokinin-mediated behaviors and receptor binding

Behavioral and receptor binding techniques were employed to evaluate the potency of CR 1409, a new analog of proglumide, as a cholecystokinin antagonist. CR 1409, at doses of 1 mg/kg i.p. in mice, effectively blocked the inhibition of feeding and exploratory behaviors induced by cholecystokinin. In rats, CR 1409 alone, at doses of 1 and 10 mg/kg, did not affect feeding or exploratory behaviors, but at 25 mg/kg alone, CR 1409 reduced food intake and exploratory behaviors, suggesting a mixed agonist-antagonist profile. On these several behavorial parameters, CR 1409 antagonized peripherally administered cholecystokinin with 10–1000 times greater potency than that reported for proglumide (Crawley et al., J. Pharmac. Exp. Ther. 236, 320–330, 1986). In binding to pancreatic cholecystokinin membranes, CR 1409 was more than 100,000-times more potent than that reported for proglumide (Rovati, Scand. J. Gastroenterol. 11, 113–118, 1976). CR 1409 inhabited binding of 125-I-cholecystokinin octapeptide in mouse parcreatic and brain membranes with IC₅₀ values of 13.7 nM and 2.6 μM, respectively, demonstrating its selectivity for peripheral-type CCK receptors.     

Dose-related involvement of CCK in bombesin-induced pancreatic growth.

We examined the role of CCK in bombesin-induced pancreatic growth in rats using the CCK receptor antagonist L-364,718. Rats (155 +/- 1 g, 8-10 per group) received subcutaneous injections every 8 h for 5 days with bombesin (0.6, 1.7 and 5 nmol/kg) or bombesin in combination with L-364,718 (1 mg/kg). After 5 days the pancreas was removed and pancreatic weight, protein content, DNA, amylase and chymotrypsin contents were determined. Bombesin produced a significant increase (48-475%) of pancreatic weight, tissue contents of protein, DNA, amylase and chymotrypsinogen (F = 82, P less than 0.001). When a large dose of bombesin (5 nmol/kg) was combined with L-364,718 a significant inhibition (up to 70%) of all tissue parameters was observed (P less than 0.001). L-364,718 did not affect the growth response to a small dose of bombesin (0.6 nmol/kg). Plasma CCK levels 15 min after a single injection of bombesin (0.6, 1.7 and 5 nmol/kg) were significantly increased in response to the 5 nmol/kg dose (2.0 +/- 0.7 to 3.4 +/- 0.8 pM, F = 6.9, P less than 0.01). No increases of CCK plasma levels were found in response to the 0.6 and 1.7 nmol/kg doses of bombesin, corresponding to the lack of effects of L-364,718 on growth parameters at these doses. Measuring the time-course of CCK plasma levels after a single injection of 5 nmol/kg bombesin revealed an increase from basal values of 1.4 +/- 0.3 pM to maximal levels of 3.5 +/- 0.5 pM after 15 min (F = 7.1, P less than 0.001). Values returned to basal after 60 min. These results suggest that low doses of bombesin act directly at the acinar cell or through release of non-CCK growth factors whereas high doses of bombesin act in part through CCK release.     

Cholecystokinin, behavioral tolerance and tumor-induced anorexia

Cholecystokinin octapeptide (CCK-8, 5 micrograms/kg, IP) was injected daily, for two 4-day periods, into rats bearing the Walker 256 carcinosarcoma (TB) and non-tumor bearing (NTB) control animals. All animals were on a 20 hr food and water deprivation schedule and monitored for food and water intake and bodyweight for 4 hr daily. Food intake was significantly reduced by the daily administration of CCK. Behavioral tolerance to CCK was not observed in either the NTB or TB rats. These results indicate that the parameters describing the phenomenon of behavioral tolerance to CCK are yet to be clearly defined and that peptides other than CCK may underlie the mechanism primarily responsible for producing anorexia associated with cancer.     

The role of some central catecholamine systems in cholecystokinin-induced satiety

Cholecystokinin (CCK), bombesin and gastrin were stereotaxically injected into catecholamine (CA) innervated areas of the lateral hypothalamus (LH), the nucleus caudatus putamen (NP) and the olfactory tubercle (OT) in male Sprague Dawley rats. Bilateral injections of 100 ng of CCK in 2 μl of vehicle into the LH produced a slight but significant decrease in food intake during the first hour of a 4 hour eating test. The other peptides when injected into any of the brain areas did not significantly alter food intake. Water intake was affected by the injection of all three hormones although differentially in all 3 sites. The observed changes in drinking were not related to the prandial characteristics of drinking typically seen in rodents. Denervation of the CA innervation of the OT, LH or NP with 6-hydroxydopamine did not change the satiety response to peripherally administered CCK displayed by intact animals. These results suggest that the satiety which occurs after the central and peripheral administration of CCK may be mediated by different mechanisms and that central CA systems may not be necessary for CCK-induced satiety to occur during natural feeding.     

Cholecystokinin and anorexia in sheep infected by the intestinal nematode Trichostrongylus colubriformis

Symons L. E. A. and Hennessy D. R. 1981. Cholecystokinin and anorexia in sheep infected by the intestinal nematode Trichostrongylus colubriformis. Internationaljournal for Parasitology11: 55–58. It was postulated that there is a correlation between anorexia in intestinal nematode infection and the plasma concentration of cholecystokinin (CCK). In the first experiment plasma concentration of CCK rose as food consumption fell until, when sheep infected with Trichostrongylus colubriformis were almost completely anorexic, it had increased by 65%. Plasma CCK and food consumption returned to pre-infection levels in from four to six days after administration of an anthelmintic. In the second experiment food consumption by uninfected sheep was reduced in the first ten minutes after intravenous infusion of 150–300 μg of the octapeptide of CCK. It was concluded that anorexia in these infections may be due to or be mediated by higher concentrations of CCK.     

The stomach, cholecystokinin, and satiety

The stomach of the rhesus monkey empties liquids in a fashion that varies with the character of the solutions. Physiological saline empties exponentially. Glucose solutions empty biphasically--rapidly for the first minutes, then slowly and proportionately to glucose concentration to deliver glucose calories through the pylorus at a regulated rate (0.4 kcal/min). This prolonged and regulated second phase of gastric emptying depends on intestinal inhibition of the stomach. Cholecystokinin (CCK), a hormone released by food in the intestine, is an inhibitor of gastric emptying. In vitro receptor autoradiography demonstrates CCK receptors to be clustered on the circular muscle of the pylorus. Exogenous CCK, in doses that inhibit gastric emptying, will reduce food intake only if combined with an infusion of saline in the stomach. These observations indicate how gastric distension can be a means for provoking satiety. The variably sustained distension produced by the stomach's slow, calorically regulated emptying could prolong intermeal intervals and thus permit high-calorie meals to inhibit further caloric intake over time. CCK, by directly inhibiting gastric emptying during a meal, could promote gastric distension and so restrict the duration and size of individual meals.     

Ventricular, paraventricular and circumventricular structures involved in peptide-induced satiety

Cholecystokinin, bombesin or gastrin (2 microliter of 50 ng/microliter) was injected stereotaxically into the paraventricular nucleus of the hypothalamus, the arcuate/ventromedial area, the subfornical organ, the area postrema and the cerebral aqueduct of Sprague-Dawley rats and the effects of these injections on food and water intake were studied. While the injection of cholecystokinin reduced food intake when it was injected into both hypothalamic loci, food and water intake were most severely affected by the injection of this peptide into the cerebral aqueduct. Bombesin reduced food intake after its injection into all areas except the subfornical organ and reliable reductions in water intake were seen after injection of this peptide into all areas except the paraventricular nucleus. Minor reductions in food intake were seen following gastrin injection into the paraventricular nucleus while increased water consumption was observed after this peptide was injected into the paraventricular nucleus and cerebral aqueduct. In a second study 6-hydroxydopamine injections (2 microliter of 8 micrograms/microliter were made into the five areas studied 10 days before animals were injected with 100 micrograms/kg of cholecystokinin (i.p.). All 6-hydroxydopamine-injected animals reduced their food and water intake in response to the cholecystokinin challenge as did intact controls. These results indicate that while the changes in food and water intake produced by the central injection of cholecystokinin, bombesin or gastrin may involve central catecholamine systems, those occurring after its systemic administration do not. Therefore, if the release of gastrointestinal peptides during natural feeding is part of a homeostatic mechanism regulating hunger and satiety, this mechanism may operate without directly involving central catecholamine systems.     

Characterization of mice lacking the gene for cholecystokinin

CCK acts peripherally as a satiating peptide released during meals in response to lipid feeding and centrally functions in the modulation of feeding, exploratory, and memory activities. The present study determined metabolic parameters, food intake, anxiety-like behaviors, and cognitive function in mice lacking the CCK gene. We studied intestinal fat absorption, body composition, and food intake of CCK knockout (CCK-KO) mice by using the noninvasive measurement of intestinal fat absorption along with quantitative magnetic resonance (QMR) imaging and the DietMax system, respectively. Additionally, exploratory and memory capacities were assessed by monitoring running wheel activity and conducting elevated plus-maze and Morris water-maze tests with these mice. Compared with wild-type (WT) littermate controls, CCK-KO mice had normal food intake, fat absorption, body weight, and body mass. CCK-KO mice ate more food than control animals during the light period and less food during the dark period. Energy expenditure was unchanged between the genotypes; however, CCK-KO mice displayed greater fatty acid oxidation. CCK-KO mice were as active as WT animals in the running wheel test. CCK-KO mice spent more time in the closed arms of an elevated plus-maze, indicative of increased anxiety. Additionally, CCK-KO mice exhibited attenuated performance in a passive avoidance task and impaired spatial memory in the Morris water maze test. We conclude that CCK is involved in metabolic rate and is important for memory and exploration. CCK is intimately involved in multiple processes related to cognitive function and food intake regulation.     

Peptidergic regulation of feeding in the dog (Canis familiaris)

Although the incidence of obesity in the domesticated dog is high, few studies have investigated the regulation of food intake in this species. In the present study we investigated the response of the dog to a number of putative satiety agents including cholecystokinin (CCK), bombesin, calcitonin and naloxone. CCK significantly suppressed food intake during a scheduled fifteen minute meal in intact dogs and in dogs receiving total subdiaphragmatic vagotomies. Emesis occurred following injection of higher doses of CCK in most dogs. Bombesin and calcitonin reduced intake in both normal and vagotomized dogs, although higher doses of calcitonin were needed to significantly suppress feeding in vagotomized dogs compared with intact animals. Naloxone reduced feeding by as much as 60% in intact and vagotomized animals. Glucagon suppressed feeding in intact dogs, but not in vagotomized animals. Somatostatin and pancreatic polypeptide did not alter food intake. Thus the domesticated dog responds somewhat differently to some neuropeptides compared with the laboratory rat stressing the importance of examining the regulation of food intake across species.     

Eating, drinking and temperature responses to intracerebroventricular cholecystokinin in the chick

The central effect of cholecystokinin-octapeptide (CCK), SQ 19,844 or sincalide, on the intake of food and water and on colonic temperature (Tc) was investigated using the broiler cockerel. Four-week old chicks were maintained in a thermoneutral environment of 23-24 degrees C. After food was removed for a 24 hr interval, CCK was infused in a volume of 10.0 microliters into the lateral cerebral ventricle (ICV) in doses ranging from 10-150 ng. Although lower doses of CCK had no effect on food intake, 100 or 150 ng of CCK significantly reduced consumption of food in a dose-dependent manner; water drinking was significantly decreased by 100 ng of CCK. In addition, CCK at doses of 100 and 150 ng prevented the slow rise in Tc observed following infusions of control CSF. This latter effect appeared to be a result of feeding activity associated with caloric intake and the heat increment in the control birds rather than a specific thermoregulatory effect. Overall, our results suggest that CCK may comprise a part of the central mechanism underlying the neural control of short term satiety in an avian species similar to that proposed for the mammal.     

The effect of peripheral administration of peptides on food intake, glucose and insulin in wolf pups

In the studies reported here we demonstrate that bombesin decreases food intake in wolf (Canis lupus) pups without altering glucose or insulin levels. A high dose of cholecystokinin-octapeptide (CCK, 5 μg/kg) decreased food intake. CCK produced a transient increase in insulin, without altering glucose. Glucagon (0.5 mg/kg) failed to decrease food intake despite producing a marked hyperglycemia and hyperinsulinemia. Calcitonin was ineffective at decreasing food intake, although it did decrease the time spent feeding. These studies suggest a potential role for peripheral peptides in food regulation in the wolf.     

Interaction of apolipoprotein AIV with cholecystokinin on the control of food intake

Apolipoprotein AIV (apo AIV) and cholecystokinin (CCK) are peptides that act both peripherally and centrally to reduce food intake by decreasing meal size. The present study examined the effects of intraperitoneally administered bolus doses of recombinant apo AIV, CCK-8, and a combination of subthreshold doses of apo AIV and CCK on 4-h food intake in rats that were fasted overnight. Apo AIV at 100 microg/kg reduced food intake significantly relative to the saline control for 1 h, as did doses of CCK-8 at or above 0.125 microg/kg. Doses of apo AIV (50 microg/kg) or CCK (0.06 microg/kg) alone had no effect on food intake. However, when these subthreshold doses of apo AIV and CCK were administered together, the combination produced a significant inhibition of food intake relative to saline controls (P < 0.001), and the duration of the effect was longer than that caused by the administration of either apo AIV or CCK alone. The satiation effect produced by CCK-8 + apo AIV was attenuated by lorglumide, a CCK1 receptor antagonist. We conclude that, whereas the intraperitoneal administration of doses of either recombinant apo AIV or CCK at or above threshold levels reduces food intake, the coadministration of subthreshold doses of the two peptides is highly satiating and works via CCK1 receptor.     

Variations in the behaviors to novel objects among five inbred strains of mice

Novelty stimuli cause various behavioral responses, such as exploration and avoidance, and contextual variables may contribute to the behavioral outputs. Here, we tried to compare the behavioral responses to novel objects of five inbred strains of mice (C57BL/6J, 129/svJae, C3H/HeJ, BALB/cJ and DBA/2J) by using a modified novel object test where a small light-weight cube wrapped with paper was presented to mice in a home cage without beddings. In response to these objects, the C57BL/6J, 129/svJae and C3H/HeJ mice showed mild exploratory behaviors, such as approaching, sniffing or brief contact. In striking contrast, the BALB/cJ and DBA/2J mice, which have been known to show high avoidance/low exploration in other behavioral paradigms, exhibited play-like secondary reactions toward the objects after initial primary exploratory behaviors. Specifically, DBA/2J mice would move the object around in the cage, holding it with their mouths, and BALB/cJ mice would gnaw the object, eventually stripping off the wrapping paper. Such behaviors decreased when similar objects were presented repeatedly. The present results suggest that active manipulations of novel objects may be a relevant parameter for measuring novelty-induced behaviors in mice and appear to be strongly influenced by genetic factors.     

Effect of lithium on secretory factors and growth stimulation by bombesin in rat pancreas and salivary glands

Lithium, a drug of choice in bipolar affective disorders, also affects the metabolism and cell proliferation in a diverse array of organisms. In this study, we investigated the effect of lithium on bombesin-mediated function in excretion and growth of the pancreas and the salivary glands. The weight, protein content, amylase concentration and salivary flow rate of the pancreas, parotid and the submandibular glands were determined in male Wistar rats after consumption of either water or lithium chloride (600 mg/l) for 14 days and each group received s.c. injection of either saline or bombesin (10 microg/kg) during the last 4 days of experiment. Our results revealed that administration of bombesin in lithium-treated group not only suppressed pancreas and parotid weight augmentation due to bombesin, but also significantly decreased pancreas growth. Chronic lithium consumption significantly inhibited the protein content augmentation due to bombesin in the salivary glands. Getting bombesin, as well as saline in lithium-treated group, resulted in notable decrease in salivary protein content. Protein content of pancreatic gland increased considerably in the bombesin-injected groups either treated with saline or lithium. In conclusion, the stimulatory effect of bombesin on the growth and protein content of the pancreas and the salivary gland was inhibited by lithium. Lithium seems to be a potent inhibitor of growth factors induced by bombesin probably through inhibiting phosphatidylinositol 4,5,bisphosphate hydrolysis.     

Feeding and selection of saccharin after injections of bombesin, LiCl, and NaCl

Rats injected with bombesin of LiCl showed similar suppression of food-deprivation-induced liquid diet intake, but only rats receiving LiCl avoided water-deprivation-induced consumption of a novel saccharin solution paired with injection. The data demonstrate that bombesin reduces feeding but does not induce conditioned aversion, and suggest that bombesin does not act to suppress food intake by production of gastrointestinal malaise.     

Cholecystokinin-induced suppression of locomotion is attenuated in capsaicin pretreated rats

Cholecystokinin (CCK), a peptide found in both gastrointestinal endocrine cells and neurons, suppresses food intake and reduces locomotor behavior when injected systemically. Both the locomotor and ingestive effects of CCK are abolished by subdiaphragmatic vagotomy. Pretreatment of adult rats with capsaicin attenuates the reduced locomotor activity and reduced food intake which normally occurs following injection of exogenous cholecystokinin. Since capsaicin damages or destroys small-diameter, unmyelinated, sensory neurons, including vagal sensory fibers, these data support the interpretation that both CCK-induced suppression of food intake and CCK-induced reduction of locomotion are mediated by fine, unmyelinated sensory neurons.