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Effect of chronic oral administration of the CCK receptor antagonist loxiglumide on exocrine and endocrine pancreas in normal rats.

CONCLUSION: In normal adult rats, administration of a low dose of loxiglumide for 7 d had no significant effect on exocrine and endocrine pancreatic function, whereas a high dose of loxiglumide decreased pancreatic enzyme output without inducing insulin resistance and diabetes mellitus. BACKGROUND: There is a possibility that chronic administration of cholecystokinin receptor antagonists not only inhibits the growth of the pancreas but also alters exocrine and endocrine pancreatic function. METHODS: Loxiglumide at a dose of 50, 100, or 200 mg/kg body weight, or the same volume of saline, was given by an orogastric tube twice daily for 7 d (13 successive times). Biochemical and functional changes were determined on d 8 at 24 h after the last administration of loxiglumide and 18 h fasting. Pancreatic exocrine and endocrine function was simultaneously determined following an intravenous injection of a mixed solution of 0.5 g/kg body weight glucose plus 100 ng/kg body weight cerulein. RESULTS: Pancreatic weight and protein content were dose-dependently decreased by loxiglumide, whereas DNA content was decreased only by the highest dose of loxiglumide. Loxiglumide caused dose-dependent decreases in pancreatic fluid and protein output. Total pancreatic insulin content in rats treated with loxiglumide was not significantly different from that in the control rats. However, insulin concentration relative to DNA content was significantly increased in rats treated with 200 mg/kg body weight loxiglumide compared with that in other groups of rats. Glucose-stimulated insulin release was significantly low in rats treated with the highest dose of loxiglumide compared with that in other groups of rats, although there was no difference of serum glucose concentrations among these four groups of rats.

Administration, Oral↗

Effect of intraduodenal infusion of tocamphyl on pancreatic exocrine secretion and gastrointestinal hormone release in rats.

Tocamphyl is a synthetic choleretic that is derived from a root extract of Curcuma longa, L. We investigated the effect of tocamphyl on pancreatic exocrine secretion and bile flow, and on the release of some gastrointestinal hormones, by administering it intraduodenally using anesthetized rats. Tocamphyl stimulated pancreatic exocrine secretion in terms of volume and amylase output in a dose-related manner. Neither a CCK-receptor antagonist, CR1505 (loxiglumide), nor atropine sulfate infused intravenously suppressed the stimulatory effects of tocamphyl on pancreatic exocrine secretion and bile flow. The stimulatory effect on bile flow was stronger than that on pancreatic exocrine secretion. Plasma secretin levels were augmented with the increasing doses of tocamphyl, but CCK levels were not. These results indicate that intraduodenally administered tocamphyl stimulates pancreatic exocrine secretion and bile flow, and suggest that the stimulatory action is, at least in part, mediated by secretin, but not by either CCK or the cholinergic pathway.

Analysis of Variance↗

Influence of the CCK-antagonist loxiglumide on bile-induced experimental pancreatitis.

The present study investigates the effect of CCK-receptor blockade on taurocholate-induced pancreatitis in rats using the potent antagonist loxiglumide. Intraperitoneal administration (50 mg/kg) of loxiglumide began 3 h before, or 10 min or 3 h after induction of pancreatitis. Mean survival times of the experimental groups were 31.2, 23.6, and 20.5 h, respectively, compared to 18.2 h for controls. Survival for 24 h after induction of pancreatitis was significantly improved when the antagonist was given 3 h before, but not in the time periods after induction. After 72 h, survival time was not significantly altered in any of the groups. Furthermore, amylase and lipase levels quantified 10 h after induction of pancreatitis in ascites, blood, or tissue did not indicate a significant difference, nor was improvement in survival seen when the CCK-antagonist was tested in rats receiving a basal treatment with intravenous volume substitution, peritoneal lavage, and protease inhibition. We conclude that CCK-receptor blockade does not improve the final outcome of bile-induced pancreatitis in the rat, even if treatment is started before induction of pancreatitis.

Animals↗

Inhibitory effects of the cholecystokinin antagonist loxiglumide on pancreatic exocrine secretion and pancreatic growth in conscious rats.

The effects of cholecystokinin (CCK) receptor antagonist Loxiglumide (CR 1505) on pancreatic exocrine secretion and growth stimulated by chronic bile-pancreatic juice diversion to the ileum were studied in conscious rats. Pancreatic secretion was measured each day at 0900 h for 7 d. Pancreatic flow and protein output were significantly increased 24 h after bile-pancreatic juice diversion. Protein output increased each successive day, reaching maximal values of 3.6-fold above basal by the 6th and 7th d of chronic bile-pancreatic juice diversion. Fluid output reached maximal values of approx. 3.5-fold above basal by the 3rd d of chronic bile-pancreatic juice diversion. Plasma CCK increased threefold above basal levels after 24 h of bile-pancreatic juice diversion and remained three- to fourfold above basal. Intragastric bolus infusion of CR 1505 (50 mg/kg) on the 7th d of chronic bile-pancreatic juice diversion inhibited pancreatic protein and fluid secretion by 80 and 75%, respectively, 60 min after administration and by 52 and 71%, respectively, 5 h later. Pancreatic wet wt after 7 d of chronic bile-pancreatic juice diversion was significantly increased by 56%, and this was completely suppressed by 50 mg/kg of CR 1505 given intragastrically every 12 h. These rests indicate that the rat with chronic bile-pancreatic juice diversion is a useful model to examine both potency and duration of the action of CCK receptor antagonists and show that CR 1505 inhibits pancreatic exocrine secretion and growth induced by endogenous CCK.

Animals↗

Pharmacological effects of oxytocin on gastric emptying and intestinal transit of a non-nutritive liquid meal in female rats.

The effects of oxytocin (OT) on gastric emptying, gastrointestinal transit, and plasma levels of cholecystokinin (CCK) were studied in female rats. Gastrointestinal motility was assessed in rats 15 min after intragastric instillation of a test meal containing charcoal and Na(2)(51)CrO(4). Gastric emptying was determined by measuring the amount of radiolabeled chromium contained in the small intestine as a percentage of the initial amount received. Gastrointestinal transit was evaluated by calculating the geometric center of distribution of the radiolabeled marker. Blood samples were collected for CCK radioimmunoassay. After administration of OT (0.2-0.8 mg/kg), gastric emptying and gastrointestinal transit were inhibited, whereas the plasma concentration of CCK was increased in a dose-dependent manner. Atosiban, an oxytocin receptor antagonist, effectively attenuated the OT- induced inhibition of gastric emptying and gastrointestinal transit. However, administration of atosiban alone had no effect on gastric emptying and gastrointestinal transit. The selective CCK(1) receptor antagonists, devazepide and lorglumide, effectively attenuated the OT-induced inhibition of gastric emptying and gastrointestinal transit. L-365, 260, a selective CCK(2) receptor antagonist, did not alter the OT-induced inhibition of gastric emptying and gastrointestinal transit. These results suggest that OT inhibits gastric emptying and gastrointestinal transit in female rats via a mechanism involving CCK stimulation and CCK(1) receptor activation.

Animals↗

Inhibitory effect of loxiglumide (CR 1505), a cholecystokinin receptor antagonist, on N-nitrosobis(2-oxopropyl) amine-induced biliary carcinogenesis in Syrian hamsters.

We evaluated the cholecystokinin (CCK) receptor antagonist loxiglumide (CR1505) for a possible inhibitory effect on biliary carcinogenesis in a hamster model. Experimental group I underwent cholecystoduodenostomy and ligation of the distal end of the common bile duct, after which the animals were injected with N-nitrosobis(2-oxopropyl)amine (BOP) alone. Group II, after the same surgical procedure as in group I, were given injections of BOP and then given loxiglumide in their diet. The sham-operated group underwent simple laparotomy and then were given injections of BOP. Loxiglumide significantly inhibited BOP carcinogenicity in the gallbladder and extrahepatic bile duct but not in the intrahepatic bile ducts or pancreas. Autoradiography showed that loxiglumide significantly suppressed (125)I-Bolton-Hanter (BH)-CCK-8 binding to CCK receptors in the gallbladder and extrahepatic bile duct but not in the liver or pancreas, and CCK binding to its receptors was observed in an area identified as cancer tissue. CCK receptor antagonists have an inhibitory effect on BOP carcinogenesis in the extrahepatic biliary tract, including the gallbladder and extrahepatic bile duct, of Syrian hamsters. The difference in the inhibitory effect of loxiglumide on biliary carcinogenesis in hamsters according to site may be due to differences in CCK receptors or the affinity of loxiglumide for such biliary tract organs. A difference between carcinogenesis in the intrahepatic bile ducts and extrahepatic biliary tract may be another reason.

Adenocarcinoma, Papillary↗

Impairment of hepatic transport processes in perfused rat liver by the specific CCK receptor antagonist loxiglumide.

The specific cholecystokinin (CCK) receptor antagonist loxiglumide has been used in several human and animal studies to investigate the role of CCK in gastrointestinal physiology. In the present study, the interference of this CCK receptor antagonist with hepatic transport processes was characterized in the perfused rat liver. Indocyanine green, an organic dye which is secreted into bile without being metabolized, was taken up in control experiments at a rate of 68.1 +/- 7.7%. The CCK receptor antagonist lowered the extraction to 0.5 +/- 2.6% (P < 0.001). The compound diminished the hepatic extraction of CCK-8 from 90.95 +/- 2.60% to 4.90 +/- 1.95% (P < 0.001) and of gastrin from 22.2 +/- 1.1% to 8.2 +/- 1.9% (P < 0.001). The hepatic extraction of lidocaine, which is metabolized by the cytochrome P450 system, was only slightly altered. For leukotrienes and taurocholate, the rate-limiting step for transport into bile is secretion across the canalicular membrane; the hepatic extraction of leukotriene D4 was markedly diminished by loxiglumide whereas the transport of taurocholate was only slightly inhibited. The present study demonstrates that the specific CCK receptor antagonist loxiglumide diminished the hepatic extraction of various substances, including peptides and organic anions. It did not interfere with the cytochrome P450 system. The pronounced reduction of hepatic uptake of indocyanine green and leukotriene may be due to an interference with the transport system of these substances in the liver.

Animals↗

Satiety effects of the type A CCK receptor antagonist loxiglumide in lean and obese women.

Several studies have demonstrated that administration of cholecystokinin (CCK) reduces food intake in several species, including humans. In animal studies CCK-receptor antagonists have been reported to increase food intake, suggesting a physiological satiety effect of CCK in these animals. In a double-blind, placebo-controlled study, we investigated the effect of the specific CCK-A receptor antagonist loxiglumide on food intake (carbohydrate-rich meal) and on subjective hunger feelings scored with visual analogue scales and food selection lists in seven healthy obese women and in seven healthy lean women. Loxiglumide was administered intravenously in a dose of 10 mg/kg ideal weight/h. For the whole group, food intake during loxiglumide (359 +/- 39 g) was not significantly different from food intake during saline infusion (333 +/- 31 g). Also, when the lean and obese subgroups were analyzed separately, no significant influence of loxiglumide on food intake was found. In addition, no significant differences in satiety scores were seen using the food selection lists or visual analogue scales. In conclusion, in the present study during infusing the CCK-A receptor antagonist loxiglumide we found no increase in preprandial satiety nor in food intake of a carbohydrate-rich meal nor in postprandial satiety in lean and obese women.

Adult↗

Cholecystokinin antagonist lorglumide reverses chronic haloperidol-induced effects on dopamine neurons.

Intravenous administration of the cholecystokinin (CCK) antagonist lorglumide (LORG) reversed chronic haloperidol (CHAL)-induced depolarization inactivation (DI) of dopamine (DA) cells in both the A9 and A10 areas. Moreover, microinjection of LORG, but not naloxone, directly into the medial nucleus accumbens (mNAc) dose-dependently reversed CHAL-induced effect. LORG injected into other brain regions was without effect. These results suggest that CCK receptors in the mNAc form an important link for maintaining CHAL-induced DI of DA cells and that CCK is involved in the therapeutic action of antipsychotic drugs.

Action Potentials↗

Cholecystokinin and its antagonist lorglumide respectively attenuate and facilitate morphine-induced inhibition of C-fiber evoked discharges of dorsal horn nociceptive neurons.

Extracellular single unit recordings were made from dorsal horn nociceptive neurons of intact, urethane-anesthetized rats during controlled electrical stimulation of the hind paw. Neither local superfusion of cholecystokinin octapeptide (CCK; 6.4 pmol to 20 nmol) nor the CCK antagonist lorglumide (LGM; 145 fmol to 145 pmol) significantly altered A- or C-fiber evoked firing or spontaneous activity. Pretreatment with CCK, however, significantly attenuated, whereas LGM enhanced, morphine-induced inhibition of C-evoked firing. These findings provide further evidence that CCK functions as a selective antagonist of opioid-induced analgesia.

Animals↗

The nature of conditioned anti-analgesia: spinal cord opiate and anti-opiate neurochemistry.

The central nervous system contains circuitry that inhibits pain sensitivity (analgesia), as well as circuitry that opposes pain inhibition (anti-analgesia). Activation of analgesia systems and anti-analgesia systems can each be brought under environmental control using classical conditioning procedures. Analgesia can be produced by cues present before and during aversive events such as electric shock, while active inhibition of analgesia comes to be produced by cues never present immediately before or during shock and therefore signal safety. We have recently reported that these analgesia and anti-analgesia systems interact at the level of the spinal cord. A series of 3 experiments were performed to examine how such interactions occur. First, potential opioid mediation of conditioned analgesia was investigated using systemic and intrathecal (i.t.) delivery of opiate antagonists. Conditioned analgesia was found to be mediated by activation of spinal mu and delta opiate receptors. Second, analgesia produced by each of these receptor subtypes was challenged by environmental signals for safety. Analgesias produced by mu and delta opiate agonists were each abolished by safety signals. Third, antagonists/antisera directed against several putative anti-opiate neurotransmitters were tested i.t. to identify which mediate conditioned anti-analgesia at the level of the spinal cord. A cholecystokinin antagonist abolished conditioned anti-analgesia. In contrast, neuropeptide FF antiserum and a kappa opiate antagonist were without effect.

Analgesia↗

Effects of cholecystokinin, caerulein and pentagastrin on electrical behavior of myenteric neurons.

Intracellular methods were used to record the electrical behavior of myenteric neurons from guinea-pig ileum in vitro. Cholecystokinin-octapeptide (CCK-8) at 1 to 100 microM in the ejection pipettes were applied to the neurons by pressure microejection. CCK-8 (0.01 to 1 microM) and caerulein (0.01 to 0.1 microM) were applied also in the superfusion solution. CCK-8, applied by either method, evoked a long-lasting depolarization of the cell membranes that was associated with an increase in the input resistance, suppression of hyperpolarizing afterpotentials and enhanced excitability. The enhanced excitability was reflected by increased probability of action potential discharge during membrane depolarization by intracellularly injected current. Caerulein evoked the same excitatory responses as CCK-8. The actions of both agents simulated slow synaptic excitation in the neurons. In another group of AH/type 2 neurons, CCK-8 evoked a long-lasting membrane hyperpolarization and decreased input resistance that mimicked stimulus-evoked slow inhibitory postsynaptic potentials. Hyperpolarizing responses were never evoked by caerulein. About 25% of tested neurons failed to respond to CCK-8 and 70% did not respond to caerulein. Pentagastrin (1 microM in the superfusion solution) did not affect the electrical behavior of the neurons. The results are consistent with a neurotransmitter role for cholecystokinin that could be either excitatory of inhibitory in the enteric nervous system.

Animals↗

The effect of loxiglumide (CR-1505) on basal and bombesin-stimulated gallbladder volume in man.

This study was undertaken in 5 normal subjects to determine the role of cholecystokinin (CCK) in the regulation of basal gallbladder volume and gallbladder contraction stimulated by infusion of bombesin. Administration of the CCK-receptor antagonist, loxiglumide (CR-1505), led to doubling of the gallbladder volume (increase 104 +/- 26%; P less than 0.05) and reduced the bombesin-stimulated gallbladder contraction from 69 +/- 17 to 19 +/- 17% (P less than 0.05). The findings provide evidence suggesting that CCK plays an important role in the regulation of basal gallbladder tone and in mediating the gallbladder contraction induced by the administration of bombesin.

Adult↗

Effect of cholecystokinin on acetylcholine turnover and dopamine release in the rat striatum and cortex.

The effect of sulfated cholecystokinin (CCK-8S) on acetylcholine turnover (TRACh) and dopamine (DA) release in the rat cerebral cortex and striatum was studied in unanaesthetized animals in vivo. CCK-8S (1 mg/kg s.c.) decreased TRACh in the fronto-parietal cortex but not in the striatum. This effect was prevented by peripheral (10 mg/kg i.p.) but not central (1 microgram i.v.t.) administration of the peripheral CCK receptor antagonist CR 1409. In a separate study, CCK-8S decreased 3-methoxytyramine (3-MT) levels (an index of DA release) in the fronto-parietal cortex and in the striatum. CR 1409 appeared to have a partial agonist action, reducing cortical and striatal 3-MT levels, and only partially reversing the effect of CCK-8S in the striatum. These data indicate that peripheral administration of CCK-8S decrease TRACh in the cortex but not in the striatum and that this action is mediated by peripheral-type CCK receptors possibly located outside the CNS. CCK-8S also reduces DA release in the cortex and in the striatum, and this effect appears to be mediated by a mechanism of action different from that modulating cortical TRACh.

Acetylcholine↗

Study into the role of cholecystokinin in bombesin-stimulated pancreatic growth in rats and hamsters.

The effects of cholecystokinin and bombesin on growth of the exocrine pancreas have been studied extensively in rats but not in hamsters. Since hamsters are frequently used for studying pancreatic carcinogenesis it seems highly relevant to determine the effects of these peptides on growth of the hamster pancreas as well. In order to determine whether or not bombesin stimulates pancreatic growth in hamsters and to investigate the role of cholecystokinin in mediating this effect, we conducted a 2-week experiment in which cholecystokinin and bombesin were administered to both rats and hamsters, either with or without lorglumide (CR-1409; a specific cholecystokinin receptor antagonist). Rats were included in the study for comparison. Cholecystokinin and bombesin were found to stimulate pancreatic growth and DNA synthesis in both species. Lorglumide did not significantly influence the effect of bombesin on pancreatic weight but did significantly inhibit DNA synthesis in both species. The effect of cholecystokinin on pancreatic weight was greater in hamsters than in rats. This effect was significantly inhibited by lorglumide in hamsters but not in rats, whereas a significant decrease in DNA content was attained in both species. Thus, this study shows marked differences between rats and hamsters in the pancreatic growth response to cholecystokinin and bombesin.

Animals↗

Role of 5-HT receptors in the effect of d-fenfluramine on gastric emptying and feeding behaviour as examined in the runway test.

In one experiment, the effect of d-fenfluramine (DF) on gastric emptying was studied in rats treated i.p. with metergoline, a non-selective serotonin (5-HT) receptor antagonist, ritanserin, a selective 5-HT2 and 5-HT1C receptor antagonist, and xylamidine, a 5-HT antagonist which has poor access to the brain. Metergoline (1 mg/kg) but not ritanserin (0.5 mg/kg) or xylamidine (3 mg/kg) blocked the effect of 2.5 mg/kg DF studied 2 and 4 h after injection. In a second experiment, we studied the ability of metergoline to antagonise the effect of DF, administered after a meal, on runway performance, food intake and gastric emptying assessed 4 h later. Metergoline at a dose of 1 mg/kg did not antagonise the effect of DF (2.5 mg/kg) on runway performance but completely blocked the effect on gastric emptying. The data clearly show that DF delays gastric emptying by indirectly activating 5-HT1 receptors; this effect is not important for the ability of DF to reduce runway performance and food intake when the drug is injected after a pre-feeding period. While there is evidence that DF hastens the termination of the meal by a 5-HT mechanism, the data suggest that DF may prolong the satiating effect of food during the post-absorptive phase by mechanisms other than 5-HT.

Animals↗

Cholecystokinin contracts isolated human and monkey iris sphincters; a study with CCK receptor antagonists.

The contractile effects of cholecystokinin (CCK) on iris sphincter and ciliary muscles from monkey and human eyes were studied using an isolated smooth muscle bath. The ability of the CCKA receptor antagonists, lorglumide and loxiglumide, to inhibit CCK-8s-induced contraction was also examined. Various neuropeptides reported to be present in capsaicin-sensitive sensory neurons were also screened for contractile effect. CCK contracted isolated human and monkey iris sphincters at nM concentrations. Both antagonists caused a rightward shift of the dose-response curve for CCK-8s on the monkey iris sphincter. The ciliary muscle from both species failed to contract in response to CCK-8s. Of the eight other neuropeptides screened on the monkey iris sphincter, only [Arg8]vasopressin elicited a weak contraction when used in microM concentrations. These results indicate that the primate iridial sphincter muscle exhibits a high sensitivity to CCK, and that CCKA receptor antagonists effectively block the CCK-induced contraction.

Aged↗

PD 135158, a CCKB/gastrin receptor antagonist, stimulates rat pancreatic enzyme secretion as a CCKA receptor agonist.

The CCKB/gastrin receptor antagonist, PD 135158 (CAM 1028), surprisingly stimulates lipase release from isolated rat pancreatic acini dose dependently in a biphasic manner, with identical efficacy but lower potency compared to cholecystokinin octapeptide (CCK-8). Half-maximal stimulation occurred at 0.6 microM and maximal secretion was induced at 50 microM. Supramaximal concentrations decreased lipase release. Acinar lipase secretion in response to 25 pM CCK-8 or 1 microM CAM-1028 was abolished by 5 microM of the specific CCKA receptor antagonist loxiglumide (CR 1505), half-maximal inhibition was observed at 0.6 microM for CCK-8 and 0.4 microM for PD 135158. These data demonstrate that the CCKB/gastrin receptor antagonist, PD 135158, acts as a full agonist at the rat pancreatic CCKA receptor.

Animals↗