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Cholecystokinin modulates neurotransmission through the dentate gyrus.

The sulfated and unsulfated cholecystokinin (CCK) octapeptide sequences and the pancreatic CCK antagonists, CR 1409 and benzotript, were administered iontophoretically while dentate gyrus granule cell activity was recorded in the anesthetized rat. During application of the compounds, the peri-stimulus time histogram (PSTH) was constructed of granule cell activity coupled to stimulation of the sciatic nerve. CCK and CR 1409, but not benzotript, were found to change significantly the PSTH by enhancing and prolonging the response to sensory stimulation. These results are interpreted as indicating that CCK can modulate impulse flow through the dentate gyrus.

Action Potentials↗

Decrease in exploratory behavior in naturally occurring cholecystokinin (CCK)-A receptor gene knockout rats.

We recently found a specific strain of rats (Otsuka Long Evans Tokushima Fatty; OLETF rats) lacking cholecystokinin (CCK)-A receptor because of a genetic abnormality. Since CCK is an abundant neurotransmitter peptide in the brain, we examined whether these animals exhibit any behavioral abnormalities by conducting open-field tests. OLETF rats showed hypolocomotor activity and a decrease in the incidence of rearing in open-field tests. CCK release from the synaptosomes, and levels of CCK and CCK-B receptor mRNAs were the same as those observed in normal rats. It is suggested that the decreased exploration in OLETF rats may be due to the lack of CCK-A receptor.

Animals↗

Cholinergic dependence of pancreatic response to cholecystokinin in rats and guinea pigs.

1. Lorglumide and atropine were used to examine the role of cholinergic mechanisms in the pancreatic secretory response to cholecystokinin in two animal species. 2. Anaesthetized rats and guinea pigs with jugular vein and pancreatic cannulae were used and the bile juice was recirculated. In the rat, the treatment with lorglumide (3 mumol/kg) as well as atropine (100 micrograms/kg) did not have effects on basal interdigestive secretion, whereas in guinea pigs only atropine decreased the protein output (41%) and the juice flow (47%) of the basal pancreatic secretion. 3. Infusion of cholecystokinin (150 pmol/kg/hr in the rat and 50 pmol/kg/hr in the guinea pig) induced a marked increase in pancreatic juice flow and protein output compared to saline controls. Pretreatment of both rat and guinea pig with lorglumide resulted in a marked attenuation of the cholecystokinin-evoked secretory response. 4. In the rats, atropine decreased the response to infusion of cholecystokinin octapeptide while this antimuscarinic agent had no effect in the response to cholecystokinin in the guinea pigs. 5. This study supports the concept that the influence of cholinergic system in pancreatic response to cholecystokinin shows interspecific differences.

Animals↗

Neuroendocrine regulation of growth hormone secretion in sheep. IV. Central and peripheral cholecystokinin.

The result of alterations in the levels of CCK, in the blood and in the cerebrospinal fluid, on the functioning of the growth hormone axis has been examined in sheep. Male Coopworth sheep of about 40 kg liveweight were given various doses of CCK either intracerebroventricularly (icv) or intravenously (iv). Other similar sheep were given various doses of a CCK antagonist (loxiglumide) by the same routes. Bolus iv administration of either 35 micrograms or 200 micrograms of CCK had no effect on plasma GH levels. When given icv, however, CCK resulted in a marked (P less than 0.01) prolonged depression in plasma GH levels. The decrease in GH secretion could be partially attenuated by concurrent administration of loxiglumide, but was completely unaffected by concurrent administration of antisomatostatin serum icv. Loxiglumide alone had no effect on plasma GH levels when given at up to 200 micrograms icv, but intravenous administration of 8 mg of the CCK antagonist resulted in an increase in plasma GH concentrations (P less than 0.05). Plasma levels of somatostatin, glucose and cortisol were unaffected by both icv and iv administration of CCK. These results show that CCK can have a strong GH-inhibiting effect in the brain. Furthermore, this effect seems to be independent of hypothalamic somatostatin, suggesting another GH-inhibiting system exists.

Animals↗

Mechanisms for pancreatic hypertrophy induced by long-term administration of bethanechol.

Mechanisms for the hypertrophy of rat pancreas induced by long-term administration of bethanechol were investigated. The administration of bethanechol, an acetylcholine receptor agonist, to male Wistar rats for 14 days induced significant increases in the pancreatic weight and contents of protein, amylase and RNA in the pancreas without altering the content of DNA and the incorporation of [3H]thymidine into DNA. Simultaneous administration of atropine with bethanechol suppressed the bethanechol-induced pancreatic hypertrophy. Long-term administration of other acetylcholine receptor agonists also showed similar effects as produced by bethanechol. CR1505 (loxiglumide; D,L-4-(3,4-dichlorobenzoyl-amino)-5-(N-3-methoxypropyl-pentylam ino)-5- oxopentanoic acid), an antagonist of cholecystokinin receptors, inhibited pancreatic growth induced by long-term administation of pentagastrin, whereas pancreatic hypertrophy induced by bethanechol was not inhibited by CR1505. These results suggest that long-term administration of bethanechol induces pancreatic hypertrophy through direct activation of muscarinic receptors in the pancreas.

Amylases↗

Estrogen and CCK1 receptor modification of mu-opioid receptor binding in the cortex of female rats.

Cholecystokinin (CCK) in the nervous system has effects opposite to those of opioids. However, the mechanism by which CCK opposes the effect of opioids at the receptor or cellular level is still unknown. In the brain, distributions of CCK receptors and opioid receptors have been demonstrated to overlap. The present study was undertaken to determine the mechanism of CCK-opioid interactions in the cortex of ovariectomized rats. Furthermore, because estrogen is a powerful regulator of CCK and opioid activity, we examined whether estrogen state also modulates the interactions of these neuropeptides. mu-Opioid (MOP) receptor binding was examined in cortical membranes that were preincubated with CCK-8S and CCK receptor agonist and antagonist followed with 3H-DAMGO. Pharmacological results revealed that CCK-8S suppressed 3H-DAMGO binding in cortical membranes of ovariectomized rats. The same result was obtained using a CCK1 receptor agonist (JMV-180), whereas a CCK2 receptor agonist (CCK-4) failed to suppress 3H-DAMGO binding. Antagonism of the CCK1 receptor by JMV-179 blocked both CCK-8S and JMV-180 suppression of 3H-DAMGO binding. Furthermore, estrogen treatment to female rats resulted in a suppression of 3H-DAMGO binding in cortical membranes. These results demonstrate an estrogen regulation of the MOP receptor and a protein-protein interaction between CCK1 receptor and MOP receptor.

Analgesics, Opioid↗

Sensitive SPE-HPLC method to determine a novel angiotensin-AT1 antagonist in biological samples.

A high-performance liquid chromatography (HPLC)-method after solid-phase extraction (SPE) has been developed in order to determine a new angiotensin-AT1 antagonist, i.e. CR 3210 (C27H24N8; MW = 460.54), 4-[4-[(2-ethyl-5,7-dimethylimidazo[4,5-b]pyridin-3-yl)methyl]phenyl]-3-(2H-tetrazol-5-yl)quinoline in rat plasma and urine after oral administration to Sprague-Dawley rats. CR 3210 and the internal standard (IS) CR 1505 (loxiglumide), i.e. 4-[(3,4-dichlorobenzoyl)amino]-5-[(3-methoxypropyl)pentylamino]-5-oxopentanoic acid, were isolated from rat urine and plasma by solid-phase extraction. The procedure was optimized regarding the sorbent extraction material, the pH in the conditioning solution, the washing step, the dry time and the type of elution solvent. The separation was performed by reversed-phase high-performance liquid chromatography with ultraviolet detection. The samples were injected onto the analytical column (Tracer Extrasil ODS1) and detected at 238 nm, giving a capacity factor of 1.87 for CR 3210 and 1.10 for the internal standard. The selectivity of the method was satisfactory. The mean recovery of CR 3210 from spiked rat plasma was 68.5 at 75 ng/ml and 80.9 at 3000 ng/ml; the mean recovery of CR 3210 from spiked rat urine was 69.9 at 75 ng/ml and 78.6 at 3000 ng/ml. The lower limit of detection (LOD) was 14 ng/ml in plasma and 22 ng/ml in urine samples. The lower limit of quantification (LOQ) was taken as 30 ng/ml, the lowest calibration standard using 500 microl rat plasma and urine. The procedures were validated according to international standards with a good reproducibility and linear response from 30 to 3000 ng/ml, for either plasma or urine. The sensitivity of the method allowed for its application to pharmacokinetic studies.

Angiotensin II Type 1 Receptor Blockers↗

Analysis of strain difference in behavior to Cholecystokinin (CCK) receptor mediated drugs in PVG hooded and Sprague-Dawley rats using elevated plus-maze test apparatus.

This study investigated the behavioral mechanisms underlying the anxiogenic, or anxiolytic mediated effects of CCK(2) receptor mediated agonist (CCK-4) and antagonist drugs (LY225910, LY288513, CR2945) in PVG hooded and Sprague-Dawley (SD) rats using the elevated plus maze test apparatus. In addition, the effects of a CCK(1) antagonist (CR1409) were investigated for its possible mediation in anxiety behavior between PVG hooded and SD rats. PVG hooded rats treated with CCK-4, decreased the time spent in the open arm and increased the time spent in the closed arm and correspondingly showed increase in the number of entries in the open arms while the number of entries in closed arm was insignificant, whereas SD rats decreased the time spent in the closed arm, while other parameters remained insignificant. PVG hooded rats administered with various CCK(2) antagonists (LY225910, LY288513, and CR2945) significantly increased the time spent in the open arm and correspondingly decreased the time spent in the closed arm, while the number of entries in the open or closed arm was insignificant, in contrast, SD rats failed to show any reliable significance. PVG hooded rats administered with the CCK(1) antagonist (CR1409), failed to show any reliable significance, in contrast, SD rats significantly increased the time spent in the open arm. The strain differences observed in this study suggests that CCK plays mainly as a neuromodulator, in which the various CCK(2) antagonists may not affect baseline anxiety state, but instead they modulate heightened states of anxiety through differential effects of CCK(1)/CCK(2) receptors.

Animals↗

Enterostatin (APGPR) enhances memory consolidation in mice.

Enterostatin (APGPR) is a pentapeptide released from its precursor protein, procolipase. We found for the first time that enterostatin has memory-enhancing activity. Enterostatin enhanced memory consolidation after central or oral administration at a dose of 10 nmol/mouse or 300 mg/kg, respectively, in a step-through type passive avoidance test in mice. The memory-enhancing activity of enterostatin was inhibited by pretreatment with lorglumide, an antagonist for cholecystokinin 1 (CCK1) receptor. However, enterostatin had no affinity for CCK receptors. These results suggest that enterostatin improves memory retention through CCK release.

Administration, Oral↗

Suppression of food intake by GI fatty acid infusions: roles of celiac vagal afferents and cholecystokinin.

We have found that jejunal infusions of long-chain fatty acids, linoleic acid (LA) and oleic acid (OA), and gastric infusions of a fatty acid ethyl ester, ethyl oleate (EO), produce long-lasting suppression of total caloric intake. This effect is not seen in response to jejunal infusions of medium-chain fatty acids or medium- or long-chain triglycerides. Multiunit recordings have shown that intestinal infusions of LA or OA strongly activate celiac vagal afferents. Truncal vagotomy (TVX) and selective celiac-branch vagotomy (CVX) are equally effective in attenuating, but not eliminating, suppression of food intake by LA and EO. These outcomes suggest that intraintestinal fatty acids reduce intake by activation of vagal mechanisms, critically involving afferent fibers within the celiac branches, as well as unidentified nonvagal mechanisms. The role of cholecystokinin (CCK) in mediating the activation of celiac vagal afferents is suggested by studies showing that (1) inhibition of food intake by CCK-8 administration is attenuated after CVX but robust after celiac-spared vagotomy (CSV), (2) multiunit activity of celiac vagal afferents is increased by CCK-8 administration, and (3) activation of celiac fibers by intestinal LA infusion is severely attenuated by the CCK(A) antagonist lorglumide.

Action Potentials↗

Cholecystokinin-induced satiety is mediated through interdependent cooperation of CCK-A and 5-HT3 receptors.

Recent evidence supports a role for the serotonin-3 (5-HT3) receptors in the modulation of cholecystokinin (CCK)-induced satiation. Likewise, 5-HT's anorectic response has been linked to recruitment of peripheral CCK-A receptors. Evidence to date, however, does not elucidate whether there is a concomitant interaction between CCK-A and 5-HT3 receptors or whether each receptor functions independently in the negative feedback control of food intake elicited by CCK. In the present study, we used selective receptor antagonists to investigate the roles of CCK-A and 5-HT3 receptors in CCK-induced satiation. Intraperitoneal administration of CCK-8 reduced 30-min 15% sucrose intake in a dose-responsive manner. Prior treatment with ondansetron (1.0 mg/kg ip), a highly selective 5-HT3 receptor antagonist, attenuated CCK-induced suppression of food intake in a dose-responsive manner. Pretreatment with lorglumide (1.0 mg/kg ip), a selective CCK-A receptor antagonist, reversed CCK-induced inhibition of sucrose intake. Finally, simultaneous blockade of CCK-A and 5-HT3 receptors by lorglumide and ondansetron, as well as concomitant administration of the two antagonists with CCK, produced a significant synergistic increase in sucrose intake compared with intakes after administration of saline, CCK, or either antagonist alone. These findings support evidence that CCK-A and 5-HT3 receptors cooperate interdependently in control of short-term food intake. Most likely, this interconnection exists through a feed-forward parallel model arising from CCK-A and 5-HT3 receptors, where activation of one system engages the other to intensify the overall satiety signal.

Animals↗

Cholecystokinin1 receptors mediate the increase in Fos-like immunoreactivity in the rat myenteric plexus following intestinal oleate infusion.

Intestinal infusion of nutrients, such as glucose and oleic acid, increase Fos-like immunoreactivity (Fos-LI) in both the enteric nervous system and neurons of the dorsal vagal complex (DVC) of the hindbrain. To test the hypothesis that increased Fos-LI in enteric neurons and the DVC, following intestinal nutrient infusions is mediated by cholecystokinin(1) receptors (CCK(1)), we counted enteric and DVC neurons that expressed Fos-LI following intestinal infusion of oleate or glucose, with and without pretreatment with the CCK(1) receptor antagonist, lorglumide. Both oleate and glucose infusions increased Fos-LI in the DVC. Oleate also increased Fos-LI in the myenteric and submucosal plexuses of the duodenum and the jejunum, but not the ileum, while glucose only increased Fos-LI in the submucosal plexus of the ileum. The CCK(1) receptor antagonist, lorglumide, abolished Fos-LI in the DVC following infusions of either oleate or glucose. In addition, lorglumide attenuated oleate-induced Fos-LI in the myenteric and submucosal plexuses of the duodenum and jejunum. However, lorglumide failed to attenuate glucose-induced Fos-LI in the submucosal plexus of the ileum. These data confirm previous reports indicating that CCK(1) receptors mediate increased DVC Fos-LI following intestinal infusion of oleate or glucose. CCK(1) receptors also contribute to increased Fos-LI in enteric neurons following intestinal oleate infusion. However, failure of lorglumide to attenuate the increase of Fos-LI in the ileal submucosal plexus following intestinal glucose suggests that some intestinal nutrients trigger Fos-LI induction via CCK(1) receptor-independent pathways.

Animals↗

Effect of deramciclane, a new 5-HT receptor antagonist, on cholecystokinin-induced changes in rat gastrointestinal function.

Recent studies suggested that serotonin receptors may be involved in modulating the actions of cholecystokinin (CCK) in the gastrointestinal tract. The present work was designed to compare the effects of deramciclane, a recently developed serotonin-2 (5-HT2A/2C) receptor antagonist, and lorglumide, a CCK(A) receptor antagonist, on exogenous and endogenous CCK-induced pancreatic enzyme secretion and pancreatic growth, as well as on the emptying of the stomach and the gallbladder. Pancreatic secretory function was tested while CCK release was evoked by diversion of bile-pancreatic juice in rats. Adaptive growth of the pancreas was induced by chronic intragastric administration of camostate, a potent synthetic trypsin inhibitor in rats. Gastric emptying of a noncaloric test meal was investigated in response to intraduodenal intralipid infusion, also in rats. In fasted mice, gallbladder emptying was examined in response to intragastric egg yolk administration. In rats, diversion of bile-pancreatic juice from the duodenum stimulated pancreatic amylase secretion. This action was blocked by deramciclane and by lorglumide. Pancreatic hypertrophy and hyperplasia induced by chronic camostate administration was also suppressed by both the serotonin- and the CCK-receptor antagonists. Intraduodenal administration of intralipid induced a significant delay in gastric emptying. This effect was inhibited by both deramciclane and lorglumide in rats. In mice, intragastric administration of egg yolk elicited an accelerated release of bile from the gallbladder. Prior treatment with either deramciclane or lorglumide abolished this response. Lorglumide was able to inhibit the functional responses elicited by exogenous CCK administration in both pancreas, stomach and gallbladder, while deramciclane was not effective under such circumstances. Our data show that deramciclane inhibited the effects of CCK on pancreatic, gastric and gallbladder function when its endogenous release was stimulated, but did not alter the effects of exogenously administered peptide. These results suggest that serotonin, primarily via 5-HT2A receptors, may modulate CCK-mediated gastrointestinal functions in rats.

Animals↗

Endogenous cholecystokinin enhances postprandial gastroesophageal reflux in humans through extrasphincteric receptors.

BACKGROUND & AIMS: Exogenous cholecystokinin (CCK) decreases lower esophageal sphincter (LES) pressure and increases transient LES relaxations (TLESRs) in humans. The aims of this study were to determine whether endogenous CCK increases gastroesophageal reflux in humans and whether this is a direct effect on the LES. METHODS: Esophageal pH, LES pressure, and gallbladder volume were measured in 8 healthy volunteers after ingestion of a 181-kcal meal alone or adding 12 g cholestyramine to increase endogenous CCK release. In 7 additional volunteers, the effect of cholestyramine was studied during intravenous perfusion of saline or the CCK-A receptor antagonist loxiglumide. In circular LES strips from 9 transplant donors, we measured the effect of CCK-8 (10(-11) to 3 x 10(-8) mol/L) on basal tension and on electrical field-induced relaxation. RESULTS: Cholestyramine increased gallbladder emptying, reflux episodes, TLESRs, and time of esophageal pH of <4. Loxiglumide inhibited postprandial gallbladder emptying, reflux episodes, TLESRs, and time of pH of <4 and prevented the decrease in LES pressure induced by cholestyramine. In vitro, CCK-8 contracted LES strips through a tetrodotoxin-insensitive pathway but did not modify electrical field-induced LES relaxations. CONCLUSIONS: Endogenous CCK enhances postprandial gastroesophageal reflux in humans by increasing the rate of TLESRs and reduces postprandial LES pressure. These actions seem mediated by extrasphincteric CCK-A receptors that override a direct contractile effect of CCK on the LES muscle.

Adult↗

Pituitary adenylate cyclase-activating peptide stimulates rat pancreatic secretion via secretin and cholecystokinin releases.

BACKGROUND & AIMS: Pituitary adenylate cyclase-activating polypeptide (PACAP) stimulates protein and/or amylase secretion from isolated rat pancreatic acini. The effect of PACAP on pancreatic secretion in vivo and its mechanism of action were studied. METHODS: Rats were prepared with pancreatic duct cannulation, pyloric ligation, and bile diversion into duodenum, and 2.5, 5, and 10 nmol/kg PACAP-27 was administered intravenously while pancreatic juice was collected for 30 minutes. In other groups of rats, the effect of 10 nmol/kg PACAP-27 was studied under the influence of either atropine; loxiglumide, an antisecretin serum; a combination of both loxiglumide and the antiserum; or a PACAP antagonist (PACAP 6-38). Plasma secretin and cholecystokinin concentrations were measured by radioimmunoassay. RESULTS: (1) PACAP dose-dependently increased pancreatic secretion of fluid, bicarbonate, and protein; (2) the increase in pancreatic secretion paralleled that of plasma secretin and cholecystokinin; (3) a combination of loxiglumide and antisecretin serum eliminated the PACAP-stimulated pancreatic secretion, whereas loxiglumide or antisecretin serum alone partially but significantly blocked pancreatic secretion; (4) atropine failed to influence PACAP-induced pancreatic secretion; and (5) PACAP antagonist profoundly suppressed the PACAP action. CONCLUSIONS: PACAP-27 dose-dependently stimulates pancreatic secretion of fluid, bicarbonate, and protein in rats. This effect is mediated by release of both secretin and cholecystokinin and is independent of cholinergic tone.

Animals↗

Fatty acid chain length determines cholecystokinin secretion and effect on human gastric motility.

BACKGROUND & AIMS: Fatty acids induce cholecystokinin (CCK) secretion and modify gastric motility, but the chain length requirements for these effects are not known. Nor is it clear whether the effects of fatty acids on gastric motility in humans are CCK mediated or directly exerted. The aim of this study was to determine the role of fatty acyl chain length in CCK secretion and in influencing gastric motility. METHODS: Fatty acids were infused into the upper gut in healthy volunteers; plasma CCK was determined by radioimmunoassay. Effects of fatty acids on antral contractility were determined by percutaneous ultrasonography; effects on proximal gastric tone were studied during fundal distention. RESULTS: Plasma CCK concentration was consistently and similarly elevated by fatty acids with a chain of 12 carbon atoms or longer, whereas those of 11 or fewer carbon atoms failed to increase plasma CCK. A 12-carbon but not a 10-carbon-long chain fatty acid reduced antral contractile amplitude, an effect that was abolished by loxiglumide (a specific CCK-A receptor antagonist). The 12-carbon fatty acid also reduced proximal gastric tone more than the 10-carbon fatty acid. CONCLUSIONS: A highly specific, chain length-sensitive fatty acid recognition system exists in the proximal gut mediating CCK secretion and gastric motility. An additional, probably CCK-independent, effect of fatty acid also regulates proximal gastric tone.

Adolescent↗

Oral glucose ingestion stimulates cholecystokinin release in normal subjects and patients with non-insulin-dependent diabetes mellitus.

The role of glucose in the regulation of plasma cholecystokinin (CCK) level was investigated in healthy control subjects and patients with non-insulin-dependent diabetes mellitus (NIDDM). Plasma CCK concentration was determined by a specific and sensitive bioassay and by a highly sensitive and reliable double-antibody radioimmunoassay using OAL-656 as an antiserum. In control subjects, ingestion of Trelan G-75 (1,200 mOsm/L,225 mL), which is equivalent to 75 g glucose as metabolic products, caused a rapid and significant increase in plasma CCK bioactivity from 1.3 +/- 0.2 to a peak of 5.8 +/- 0.6 pmol/L and immunoreactive CCK concentration from 1.2 +/- 0.1 to 4.6 +/- 0.6 pmol/L. Ingestion of 75 g glucose in 225 mL water (33.3% solution) increased plasma CCK bioactivity to a similar degree to that observed following Trelan G-75 (peak response, 4.5 +/- 0.4 pmol/L). The same volume of 0.9% NaCl solution or water failed to increase plasma CCK concentration. A smaller dose of glucose (50 b/150 mL water) increased plasma CCK concentration, although the peak level (3.0 +/- 0.5 pmol/L) was less than that observed following 75 g glucose. In patients with NIDDM, Trelan G-75 ingestion increased CCK concentration, but the peak level was lower, albeit insignificantly, than that of normal subjects. When the maximal increment of plasma CCK above the basal value was compared between control and NIDDM subjects, the differences were statistically significant (NIDDM, 3.6 +/- 0.1 pmol/L; control, 5.0 +/- 0.4; P < .01). However, integrated CCK responses to Trelan G-75 in NIDDM (165.8 +/- 15.5 pmol/120 min) were not significantly different from those in control subjects (189.8 +/- 15.9 pmol/120 min). Peak CCK bioactivity occurred within 10 to 30 minutes of ingestion, preceding the increase in glucose and insulin. These results suggest a possible effect of CCK on insulin release in humans, and that the CCK secretory response to glucose in well-controlled diabetic patients is not significantly altered.

Administration, Oral↗