Effects Of Cholecystokinin Octapeptide Research Articles

The therapeutic effects of cholecystokinin octapeptide on rat liver and kidney microcirculation disorder in endotoxic shock

Objectives: Our previous studies demonstrated that pretreatment with cholecystokinin octapeptide (CCK-8) could alleviate endothelial cell injury and reverse abnormal vascular reactivity as well as reduce LPS-induced inflammation cascades, which suggested that CCK-8 plays a potential role in anti-endotoxic shock. The present study aimed to determine the therapeutic effects of CCK-8 on rat liver and kidney microcirculatory perfusion disorder under endotoxic shock (ES) conditions.Materials and Methods: Sprague-Dawley rats were induced to lethal endotoxic shock by an injection of LPS. CCK-8 was administered 30 min after LPS injection. Either a specific CCK-1R antagonist or CCK-2R antagonist was injected before CCK-8 treatment. The mean arterial pressure (MAP), liver and kidney microcirculatory perfusion, and heart rate (HR) were recorded with a multi-channel data acquisition system. The serum concentrations of alanine aminotransferase (ALT) and creatinine (Cr) were measured, and the histopathological changes in the liver and kidney were also observed.Results: Administration of CCK-8 significantly delayed the LPS-induced decreases in not only the liver and kidney microcirculation perfusion but also the HR. The pathology changes induced by LPS in the liver and kidney tissues were significantly mitigated in the LPS + CCK-8 group. The levels of ALT and Cr in the serum of the LPS + CCK-8 group were obviously lower than those in the LPS group. In addition, the specific antagonist at the CCK-2 receptor (CCK-2R) abrogated the action of CCK-8 significantly.Conclusions: These results indicated that CCK-8 has potential therapeutic effects on microcirculation failure in an ES rat model via the CCK-2 receptor.

Role of Calcium in Activation of Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels Caused by Cholecystokinin Octapeptide in Interstitial Cells of Cajal

Background: Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate pacemaker activity in some cardiac cells and neurons. Little is known about the effects of cholecystokinin octapeptide (CCK-8) on HCN channels and excitability of murine interstitial cells of Cajal (ICCs). Methods: In the present study, the effects and mechanisms of CCK-8 on HCN channels were investigated by measuring mechanical contraction of smooth muscle strips and ionic channels of ICCs in murine gastric antrum. Results: Sulfated CCK-8 (CCK-8S) was used, and we found that CCK-8S increased the contraction of smooth muscle strips in the gastric antrum, which could be suppressed by specific HCN channel blockers CsCl and ZD7288. Extracellular calcium could also intensify the contraction. Under the same conditions, when antral strips were exposed to calcium ion (Ca²⁺)-free solution, no significant changes could be recorded with CCK-8S or ZD7288. Isolated ICCs from the murine gastric antrum identified by specific c-Kit antibody primers were chosen for electrophysiological recordings. HCN current (I_h) of cultured ICCs was studied by whole-cell patch clamp techniques. A spontaneous transient inward current was recorded in ICCs, which could be inhibited by addition of CsCl and ZD7288; the current proved to be I_h. CCK-8S-facilitated I_h in cultured ICCs could be inhibited by CsCl and ZD7288. When cultured ICCs were exposed to Ca²⁺-free solution, no significant changes could be recorded by application of CCK-8S on I_h, which proved extracellular calcium might have an excitatory effect on HCN channels. Conclusion: We demonstrate that HCN channels are present in ICCs in the murine gastric antrum; they might be an important regulator of ICC excitability and pacemaker activity and are strongly affected by CCK-8S. Extracellular calcium might be a trigger in the activation of HCN channels caused by CCK-8S in cultured ICCs.

The Effect of Cholecystokinin Octapeptide on Lipopolysaccharide-induced Sickness Behavior and Peripheral Cytokine Secretion

Cytokines have been considered to be involved in the pathology of sickness behavior,but the role of peripheral cytokines in the pathology of sickness behavior is still elusive.Cholecystokinin octapeptide(CCK-8) has been proved to inhibit the lipopolysaccharide(LPS)-induced secretion of peripheral proinflammatory cytokines in rats.Aim:To investigate the role of peripheral cytokines in the pathology of sickness behavior.Methods:The experiment included two parts.In Experiment 1,forty-six rats were randomly divided into 4 groups:control,LPS,CCK-40+LPS and CCK-40,each group comprised twelve rats except ten rats for the control group,and in Experiment 2 forty-eight rats were randomly divided into six groups:control,LPS,CCK-20+LPS,CCK-40+LPS,CCK-80+LPS,CCK-120+LPS,each group comprised eight rats.The CCK groups were injected with different dosages of CCK-8 solution(20μg/kg,40μg/kg,80μg/kg and 120μg/kg doses respectively,i.p.) half an hour before the injection of LPS(200μg/kg,i.p.),and then 2 hours after the LPS injection,the sickness behavior was measured in behavioral experiments(including the sugar-water consumption test,open field test,and elevated plus maze test),and the cytokines in serum were analyzed by immunoassays.Results:LPS induced sickness behavior:LPS group consumed less sugar water and exhibited less activities in open field test and elevated plus maze test when compared with the controls;LPS also significantly increased cytokine production including IL-1β,IL-6 and TNF-α.However,the LPS-induced sickness behavior could not be attenuated by CCK-8,though CCK-8 significantly inhibited the LPS-induced proinflammatory cytokines of IL-1β,IL-6 and TNF-α compared to the LPS group.Conclusion:The inhibition of the secretion of peripheral proinflammatory cytokines can not antagonize the lipopolysaccharide-induced sickness behavior.The peripheral proinflammatory cytokines might be not directly responsible for the sickness behavior.The cytokines acting in brain may be more related to the sickness behavior,which needs further investigation.

Effects of cholecystokinin octapeptide on the contractile activity of guinea-pig colonic smooth muscles, L-type calcium currents and membrane potentials of myocytes

To investigate the effects and mechanism of cholecystokinin octapeptide (CCK-8S) on the contractile activity of smooth muscles, L-type calcium current and membrane potentials of proximal colon myocytes in guinea pig. (1) Strips of proximal colon were obtained from adult guinea pigs. The contraction of these stripes was measured by a RM6240 multi-channel physiological signal system. (2) Suspension of single smooth muscle cells (SMCs) were obtained from proximal colon and isolated by enzymatic digestion. The effect of CCK-8S on intracellular calcium concentration ([Ca(2+)]i) of SMCs was examined by fura-2-loaded microfluorimetric measurement. (3) Resting potential (RP), action potential (AP) and L-type calcium current (I(Ca-L)) were recorded by patch-clamp technique. (1) The contractile amplitude and frequency of muscle stripes enhanced by CCK-8S (10(-7) mol/L) were (149 ± 12)% and (132 ± 13)% respectively of those of control group (all P < 0.05). They were significantly attenuated by pretreating strips with CCK1 receptor antagonist devazepide (10(-7) mol/L), L-type calcium channel blocker nifedipine (10(-5) mol/L), Ca(2+)-ATPase inhibitor TG (thapsigargin) (10(-5) mol/L) and BA (boric acid) (10(-5) mol/L) respectively. (2) [Ca(2+)]i of SMCs intensified by CCK-8S was (738 ± 24)% of that of control group. And it was inhibited by pretreating SMCs with devazepide (all P < 0.05). (3) After the superfusion of CCK-8S, RP depolarized to (52 ± 9)%, the exogenously stimulated peak values of AP rose to (140 ± 4)% and fast repolarization time of AP decreased to (61 ± 13)% (all P < 0.05). They were significantly inhibited when these cells were pretreated with devazepide and/or nifedipine (n = 8, P < 0.05 for each group) whereas CI 988 had little effect. (4) The CCK-8S-evoked I(Ca-L) of SMCs at the voltage of + 10 mV was boosted to (138 ± 7)%. Such an effect was suppressed by a pretreatment with nifedipine, devazepide, TG and BA respectively. In the presence of an inhibitor of inositol 1,4,5-trisphosphate (IP3) receptors, heparin (10(-6) mol/L) and an protein kinase C (PKC) inhibitor, saurosporine (10(-6) mol/L), CCK-8S did not significantly intensify I(Ca-L) (all P > 0.05). CCK-8S promotes proximal colon contraction by CCK1 receptors through the activation of IP3-mediated PKC pathway.

Effects of cholecystokinin-octapeptide and cerulein on small-intestinal motility in sheep

Cholecystokinin (CCK) affects the intestinal motility but in ruminants the question has not been entirely explored. The aim of this study was to examine the precise effects of CCK-octapeptide (CCK-OP)&lt;br /&gt;and its amphibian analogue, cerulein, on duodenal motor activity in unfasted rams in the course of chronic experiments. Five rams underwent the implantation of a strain gauge force transducer to the duodenal wall, and &amp;ndash; additionally &amp;ndash; the bipolar platinum electrodes to the duodenal bulb, distal duodenum, near the strain gauge force transducer, and proximal jejunum. During continuous motor recordings, 0.15M NaCl or CCK peptides were administrated intravenously. Injections of CCK-OP at doses of 20 (over 30 s), 200 (over 30 or 60 s), and 2 000 (over 30, 60, or 120 s) ng/kg of body weight and injections of cerulein at doses of 1, 10, or 100 ng/kg (given over the same periods) were each administered in the course of duodenal phase 1, 2a, or 2b of the migrating motor complex (MMC), i.e. 5 min after the onset of each phase. Injections of the smallest doses of CCK peptides exerted a slight and mostly insignificant effect on the duodenal areas under contraction (AUC). In the duodenum, the moderate doses of the hormones evoked short stimulatory effects followed by longer inhibitory biphasic effects on AUC. These effects were inversely related to the duration of the hormone injection. It is concluded that CCK evokes stimulatory and inhibitory (biphasic) physiological effects on duodenal motility in sheep. &amp;nbsp;

Dose-related effects of cholecystokinin octapeptide administered during various phases of the migrating motor complex on small-intestinal motility in sheep

Cholecystokinin (CCK) may affect intestinal motility, but in ruminants its precise effects have not been entirely explored. The aim of this study was to examine the effects of CCK-octapeptide (CCK-OP) on small-intestinal myoelectric activity in rams in the course of chronic experiments. Five rams underwent implantation of bipolar platinum electrodes to the duodenal bulb, distal duodenum, and jejunum as well as a strain gauge force transducer attached near the duodenal electrode. During continuous myoelectric recordings, 0.15 M NaCl or CCK-OP were injected slowly into the jugular vein. Injections of CCK-OP at doses of 20 (over 30 s), 200 (over 30 or 60 s) and 2000 (over 30, 60 or 120 s) ng/kg of body weight were each administered 5 or 30-40 min after the onset of the duodenal phase 1 or phase 2 of the migrating myoelectric complex (MMC), respectively. Most of these CCK doses were considered physiological. Injections of the smallest dose of CCK-OP exerted a slight and mostly insignificant inhibitory effect on the duodenal bulb and the duodenal myoelectric activity index (MAI) values. In the duodenal bulb, the effects of CCK-OP on myoelectric activity were dose dependent and closely related to the phase of the MMC. In the duodenum, the high dose of the hormone evoked short stimulatory and longer inhibitory biphasic effects on the MAI. These effects were inversely related to the duration of the hormone injection. It is concluded that CCK evokes a physiological stimulatory and inhibitory (biphasic) effect on the duodenal bulb and duodenal motility in sheep, with the inhibitory effect of the hormone being more pronounced in the duodenal bulb than in the duodenum. These effects were related to the CCK dose and the MMC phase. Therefore, CCK is an important regulator of upper small bowel motility in sheep.

The effect of cholecystokinin octapeptide upon the migrating myoelectric complex in the ovine small bowel

There is no evident and precise data regarding the effect of cholecystokinin octapeptide (CCK-OP) on the migrating myoelectric complex (MMC) in sheep. Thus, in five rams seven bipolar platinum electrodes were implanted in the abomasal antrum and entire small intestine. The strain gauge force transducer was also attached near the duodenal electrode in three of these animals. During the experiments the myoelectric and motor activity was continuously recorded in fasted and non-fasted sheep. During the recordings two normal consecutive phases 3 of the MMC were recorded. Then, slow injections of CCK-OP of 0.02; 0.2 and 2.0 _g/kg of body weight were given intravenously during phase 1, 2a or 2b of the MMC, identified in the duodenum, until next two consecutive phases 3 MMC were recorded. The moderate dose of CCK-OP administered during phase 2a in non-fasted animals shortened the MMC cycles significantly while the highest dose of the hormone increased the cycle duration and inhibited phase 3 MMC in the duodenum. No such effect was observed in the jejunum. However, duration of phase 3 in this region was decreased mostly by the highest dose of CCK-OP. It can be concluded that CCK inhibits the MMC in ovine small bowel and its effect in the duodenum is most pronounced.

Effect of Cholecystokinin-Octapeptide and Cerulein on Phasic and Tonic Components in Ovine Duodenum with Special Reference to the 'Minute Rhythm'

Cholecystokinin (CCK) can affect phasic contractions and the minute rhythm (MR) in ovine duodenum but its effect on the tonic component remains unclear. Thus, the aim of this study was to assess whether the hormone exerts significant changes on phasic and tonic components of the duodenal motor activity and on phasic and tonic components of the duodenal MR. Mechanical and electrical activities of the duodenum were recorded in four sheep before and after slow intravenous cholecystokinin octapeptide (CCK-OP, doses 20, 200 and 2000 ng/kg b.w.) and cerulein (doses 1, 10 and 100 ng/kg b.w.) administration in the course of phase 2b of the migrating motor complex. During 5-20-minute periods the area under contraction curve for phasic, tonic and total motor activity was measured for the whole curve and separately for the MR- related activity. It was found that both CCK peptides stimulate phasic and tonic components of the duodenal motor activity as well as both these components of the duodenal MR. The effect of CCK peptides on the tonic component was stronger than on the phasic component. These effects were similar in non-fasted and fasted animals. CCK-OP evoked slightly greater effect than cerulein. The effects of these CCK peptides on phasic and tonic components of the MR were similar. It is concluded that CCK-OP and cerulein stimulate both phasic and tonic components of the duodenal motor activity and phasic and tonic components related to the MR in sheep.

Mechanism of exocrine pancreatic insufficiency in streptozotocin-induced diabetes mellitus in rat: effect of cholecystokinin-octapeptide.

This study investigated the effects of cholecystokinin-octapeptide (CCK-8) on pancreatic juice flow and its contents, and on cytosolic calcium (Ca2+) and magnesium (Mg2+) levels in streptozotocin (STZ)-induced diabetic rats compared to healthy age-matched controls. Animals were rendered diabetic by a single injection of STZ (60 mg kg(-1), I.P.). Age-matched control rats obtained an equivalent volume of citrate buffer. Seven weeks later, animals were either anaesthetised (1 g kg(-1) urethane; IP) for the measurement of pancreatic juice flow or humanely killed and the pancreas isolated for the measurements of cytosolic Ca2+ and Mg2+ levels. Non-fasting blood glucose levels in control and diabetic rats were 92.40 +/- 2.42 mg dl(-1) (n = 44) and >500 mg dl(-1) (n = 27), respectively. Resting (basal) pancreatic juice flow in control and diabetic anaesthetised rats was 0.56 +/- 0.05 ul min(-1) (n = 10) and 1.28 +/- 0.16 ul min(-1) (n = 8). CCK-8 infusion resulted in a significant (p < 0.05) increase in pancreatic juice flow in control animals compared to a much larger increase in diabetic rats. In contrast, CCK-8 evoked significant (p < 0.05) increases in protein output and amylase secretion in control rats compared to much reduced responses in diabetic animals. Basal [Ca2+]i in control and diabetic fura-2-loaded acinar cells was 109.40 +/- 15.41 nM (n = 15) and 130.62 +/- 17.66 nM (n = 8), respectively. CCK-8 (10(-8)M) induced a peak response of 436.55 +/- 36.54 nM (n = 15) and 409.31 +/- 34.64 nM (n = 8) in control and diabetic cells, respectively. Basal [Mg2+]i in control and diabetic magfura-2-loaded acinar cells was 0.96 +/- 0.06 nM (n = 18) and 0.86 +/- 0.04 nM (n = 10). In the presence of CCK-8 (10(-8)) [Mg2+]i in control and diabetic cells was 0.80 +/- 0.05 nM (n = 18) and 0.60 +/- 0.02 nM (n = 10), respectively. The results indicate that diabetes-induced pancreatic insufficiency may be associated with derangements in cellular Ca2+ and Mg2+ homeostasis.

Levels of catecholamines and 5-hydroxytryptamine and eating behavior in lateral hypothalamic aphagic rats

Male rats injected with 6-hydroxydopamine in the lateral hypothalamus did not eat food pellets but ingested an intraorally infused nutritive solution. This 'intraoral intake test' activates consummatory ingestive behavior, the responses used to ingest food, but ignores appetitive ingestive behavior. If given three daily intraoral intake tests, 6-hydroxydopamine-treated rats defended a low body weight, and they were oversensitive to the inhibitory effect of cholecystokinin octapeptide. The concentration of dopamine in the dorsal and ventral striatum was decreased by > 75%, 13 days after the 6-hydroxydopamine treatment, whereas the effect in the frontal cortex was less pronounced. The concentration of noradrenaline and 5-hydroxytryptamine was somewhat less affected, while that of glutamate and cholecystokinin octapeptide was markedly less affected by the 6-hydroxydopamine lesion. Feeding behavior and body weight regulatory competence is, thus, in part retained in rats with massive damage to dopamine neural networks. It is suggested that these networks are not required for consummatory but for appetitive ingestive behavior and for proper perception of the sensory and hormonal signals from the gastrointestinal tract.

Effects of cholecystokinin octapeptide on the exocrine pancreas in a new rat model of type 2 diabetes

We investigated the effects of increasing concentrations of cholecystokinin octapeptide (CCK-8) on the exocrine pancreas of a new model of type 2 diabetic rats due to the partial protection exerted by nicotinamide against the β-cytotoxic effect of streptozotocin. CCK-8, administered for 8 successive days, exerted a biphasic action on the growth of the pancreas in non-diabetic and type 2 diabetic rats; however, the latter were less sensitive to CCK-8. Similar results were obtained in vitro by measuring the uptake of 5-bromo-2′-deoxyuridine (BrdU) in cultured isolated acinar cells. This effect was completely blocked by 3 S(−)( N′-2,3-dihydro-1-methyl-2-oxo5-phenyl-1 H-1,4-benzo-diazepin-3-yl)-1 H-indole-2-carboxamide (L 364,718; a CCK 1 receptor antagonist) but not by (3 R)-3[ N′-(3-methylphenyl)ureido]-1,3-dihydro-1-methyl-5-phenyl-2 H1,4-benzo-diazepin-2-one (L 365,260; a CCK 2 receptor antagonist), suggesting a direct effect via CCK 1 receptors. Binding studies showed that these effects were mediated by a single class of low-affinity CCK 1 receptors in diabetic rats and two classes of CCK-8 binding sites (with high and low affinity) in non-diabetic rats. Thus, in our new type 2 diabetes model, the loss of sensitivity of the pancreas to CCK-8 could be attributed to the loss of CCK 1 receptors of high affinity.

Effect of Truncal Vagotomy on Sphincter of Oddi Cyclic Motility in Conscious Dogs

To evaluate the effects of truncal vagotomy at the diaphragmatic level on the sphincter of Oddi (SO) motility. Cholelithiasis is a well-known late complication after gastrectomy and/or vagotomy. The mechanism of gallstone formation is only partly understood, and few studies address the effects of vagotomy on SO cyclic motility in conscious subjects. In conscious dogs, SO motility was recorded by retrograde infusion manometry through a duodenal cannula before and after bilateral truncal vagotomy at the diaphragmatic level. Effects of cholecystokinin-octapeptide and feeding were also evaluated before and after vagotomy. SO cyclic motility and the gastroduodenal migrating motor complex continued to occur during postvagotomy fasting. Intermittent inhibitions of the SO and duodenal contractions disappeared during phase 3 of the migrating motor complex. SO basal pressure significantly decreased, whereas the amplitude significantly increased. Cholecystokinin-octapeptide inhibited SO contractions before and after vagotomy. The amplitude of SO contractions increased and their frequency decreased after feeding; however, these effects disappeared after vagotomy. SO cyclic motility and the effects of feeding change after truncal vagotomy at the diaphragmatic level. These facts may at least partly explain gallstone formation after gastric surgery and/or vagotomy.

Biliary sphincter motility after neural isolation of the pancreatoduodenal region in conscious dogs

Background. Several neural and hormonal factors are known to affect the motility of the sphincter of Oddi. However, the precise mechanisms of the control of sphincter motility have not been completely explored. We investigated the relationship of canine biliary sphincter motility when it is extrinsically denervated by neural isolation of the pancreatoduodenal region. Methods. Interdigestive and postprandial sphincter motility in a denervated pancreatoduodenal segment and effects of cholecystokinin-octapeptide were studied in 7 conscious dogs. Data were compared with those of 7 neurally intact control dogs. Results. After extrinsic denervation of the pancreatoduodenal region, sphincter motility exerted a cyclic change in concert with the duodenal myoelectric cycles; this change involved short cyclic bursts of motor activity, which gradually increased in intensity. The increase in the cyclic bursts of motor activity was also cyclic and associated with an increase in the plasma motilin concentration. Neural isolation of the pancreatoduodenal region increased sphincter basal pressure and motility index (integral per minute). In the denervated biliary sphincter, the feeding pattern and temporary inhibitory effect of feeding, as seen in controls, were absent, which suggests the role of extrinsic nerves in delivering bile into the duodenum after feeding. In the denervated dogs, cholecystokinin-octapeptide caused excitation of the sphincter activity, instead of relaxation observed in controls. Conclusions. Extrinsic innervation to the pancreatoduodenal region has an inhibitory effect on biliary sphincter motility. Abnormalities in extrinsic innervation to the biliary sphincter might increase the resistance of the sphincter to the bile flow and induce bile stagnation. (Surgery 2002;131:139-48.)

Effect of cholecystokinin octapeptide on tumor necrosis factor alpha transcription and nuclear factor-kappaB activity induced by lipopolysaccharide in rat pulmonary interstitial macrophages.

To elucidate the anti-inflammatory mechanism of an intestinal neuropeptide, sulfated cholecystokinin octapeptide (sCCK-8), the effects of sCCK-8 on lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF-alpha) mRNA expression and NF-kappaB activity in pulmonary interstitial macrophages (PIMs) were studied. PIMs from rat were stimulated with LPS (1 mg.L(-1)) in the presence or absence of sCCK-8 (10(-8)-10(-6)mol.L(-1)) or/and CCK receptor antagonist proglumide (2 mg.L(-1)). The expression of TNF-alpha mRNA was assayed by reverse transcription polymerase chain reaction (RT-PCR) at 3h of the stimulation, and nuclear factor-kappaB (NF-kappaB) binding activity was analyzed by electrophoretic mobility shift assay (EMSA) at 1 h of stimulation. The IkappaBalpha protein level in the cytoplasma at 30 min of the stimulation was detected by Western blot. sCCK-8, at concentrations from 10(-8) mol.L(-1) to 10(-6) mol.L(-1) obviously inhibited LPS-induced TNF-alpha mRNA expression and NF-kappaB binding activity in a dose-dependent manner, P<0.05, P<0.01. Stimulation PIMs with LPS resulted in a reduction of IkappaBalpha protein level, P<0.01, which was elevated by sCCK-8, P<0.05. The effects of sCCK-8 on NF-kappaB activity and IkappaB protein level were attenuated by CCK receptor antagonist proglumide, P<0.01. sCCK-8 inhibits LPS-induced TNF-alpha mRNA expression by regulating NF-kappaB activity in rat PIMs, which is mediated through CCK receptors and inhibiting IkappaB-alpha degradation. This represents one of the anti-inflammatory mechanisms of sCCK-8.

Functional CCK-A and Y2 receptors in guinea pig esophagus

Effects of cholecystokinin octapeptide (CCK-8), peptide YY (PYY), neuropeptide Y (NPY) and their analogs on muscle contractions of esophageal strips were investigated. CCK-8-induced a tetrodotoxin and atropine-sensitive contraction. The relative potencies for CCK related peptides to induce contractions were CCK-8>desulfated CCK-8>gastrin-17-I. The CCK-A receptor antagonist L-364,718 was >300-fold more potent than the CCK-B receptor antagonist L-365,260 at inhibiting CCK-8-induced contraction. These indicate that neural CCK-A receptors mediate this contraction. PYY or NPY did not cause muscle contraction or inhibit muscle contraction induced by carbachol, endothelin-1 or KCl. However, both PYY and NPY concentration-dependently inhibited contraction induced by CCK-8. This inhibition was not affected by nitric oxide (NO) synthase inhibitors l-NMMA or l-NAME. The relative potencies for PYY related peptides to inhibit CCK-8-induced contraction were PYY>NPY>NPY13–36>[Leu 31, Pro 34]NPY>pancreatic polypeptide (PP). We conclude that CCK interacts with neural CCK-A receptors to cause esophageal muscle contraction. PYY and NPY interact with Y2 receptors to inhibit this CCK-induced muscle contraction by an effect not related to NO.

Involvement of CCK in the Paraventricular Nucleus of the Hypothalamus in the CNS Regulation of Colonic Motility

The effects of cholecystokinin octapeptide (CCK₈), the CCK-A receptor antagonist, MK-329, and the CCK-B receptor antagonist, L-365, 260, microinfused into the paraventricular nucleus of hypothalamus (PVN) on colonic motor function was investigated in awake rats, chronically implanted with a microinjection cannula into the PVN and a catheter into the proximal colon. In fasted rats, bilateral microinfusion of CCK₈ at doses of 1.5 and 3.0 μg/rat into the PVN stimulated colonic transit, as shown by a significant increase in the geometric center by 47 and 54%, respectively. This effect of CCK₈ was site-specific to the PVN, since microinjection of the peptide into sites outside of but adjacent to PVN had no effect. In non-fasted rats, L-365,260 bilaterally microinjected into the PVN at a dose of 1.5 μg/rat inhibited propulsive colonic motor function; colonic transit time significantly increased by 73% in comparison to the control condition. Microinfusion of the CCK-A antagonist into in the PVN did not affect colonic transit. These results show that the PVN is a responsive site for the central CCK₈-induced modulation of colonic motility. The data suggest, that endogenous CCK in the paraventricular nucleus of the hypothalamus unfolds a stimulatory effect on colonic transit through action on CCK-B receptors.

Effects of cholecystokinin on liquid diet intake of early weaned piglets

The effect of cholecystokinin octapeptide (CCK-8) on the consumption of a liquid diet was investigated in 10 piglets, weaned on Day 1, housed individually in cages, and offered a commercial diet for suckling from feeding bottles nine times a day at 2-h intervals with an 8-h break during the night. CCK-8 was administered to piglets ( n = 5) on Days 2, 4, 6, 8, 10, 12, 20, and 23 in single intraperitoneal doses of 4 μg·kg −1 in saline, 5–7 min before the first morning feeding at 0600 h. The relative diet intake in CCK-treated animals was reduced significantly ( p < 0.05) on Days 2, 4, 6, 8, 10, 12, and 23 compared to saline-treated controls, and on Days 2, 4, 6, 8, 10, 12, and 23 when the consumption at 0600 and 0800 h in CCK-treated piglets was compared. Our data support the notion that the short-term mechanisms involved in food intake control of piglets are relatively complex and operative at the time of birth, and that CCK plays a role in their food intake regulatory cascade.

Effects of cholecystokinin octapeptide on a pancreatic acinar carcinoma in the rat.

To investigate the effects of increasing concentrations of cholecystokinin octapeptide (CCK-8) on a pancreatic acinar adenocarcinoma. Growth of the tumour was estimated in vivo on rats bearing a subcutaneous pancreatic carcinoma, and in vitro on primary cultured tumour cells. CCK receptors were characterized by binding assays. CCK-8, administered for 12 successive days, exerted a biphasic action on tumour growth: a dose-dependent stimulation with low doses (0.1 and 0.5 microg/kg) and inhibition with high doses (2 and 4 microg/ kg) as shown by respective increases and decreases in tumor volume, protein, RNA and amylase contents. In cell cultures, [3H]thymidine incorporation was dose-dependently increased with 10-(10) to 10(-8) M CCK-8 and inhibited with 10(-7) M. Both effects were completely suppressed by the CCK-receptor antagonists CR 1409 and L 364,718 (10(-4) M). Binding studies showed the overexpression of two classes of CCK-A receptors of low and high affinity when compared to the normal pancreas which was less sensitive to CCK-8. CCK-8 exerts a biphasic growth response on the acinar pancreatic carcinoma, mediated by two classes of CCK-A receptors overexpressed in the tumour.

Electrophysiological changes in rat hippocampal pyramidal neurons produced by cholecystokinin octapeptide

Effects of cholecystokinin octapeptide (CCK-8) were investigated in CA1 pyramidal neurons of rat hippocampal slice cultures using the whole-cell patch-clamp technique. In the current-clamp mode, CCK-8 (100 nM) produced slight depolarizaton (2.1±0.3 mV) and reduced the amplitude of afterhyperpolarization following a train of spikes. CCK-8 (10 nM–1 μM) concentration-dependently reduced the amplitude of afterhyperpolarization. CCK-4, a selective agonist for CCK B receptors, also attenuated the amplitude of afterhyperpolarization. CCK-8-induced suppression was completely abolished by (+)L-365,260, a selective CCK B receptor antagonist, but not by (−)L-364,718, a selective CCK A receptor antagonist. Similarly, CCK-8 reduced the tail currents following a depolarizing pulse. The tail currents were characterized as Ca 2+-activated K + currents. When neurons were held at a holding potential of −40 mV, CCK-8 elicited inward currents with a reduction of membrane conductance. This current had a relatively linear current–voltage relationship and was reversed in polarity at membrane potentials close to the K + equilibrium potential, suggesting that CCK-8 decreases leak K + currents. Moreover, voltage-activated Ca 2+ currents were partially blocked by CCK-8, and this effect was enhanced by intracellular application of GTP γS (300 μM) or a protein phosphatase inhibitor, okadaic acid (100 nM), and attenuated by GDP βS (300 μM) or a protein kinase inhibitor, staurosporin (400 nM). In acutely-prepared hippocampal slices from neonatal rats, CCK-8 also depolarized CA1 pyramidal neurons and suppressed afterhyperpolarization following a train of action potentials. These results indicate that CCK-8 increases neuronal excitability by suppressing leak K + currents and Ca 2+-activated K + currents in CA1 pyramidal neurons of the hippocampus through activation of CCK B receptors.

Direct contractile effect of cholecystokinin octapeptide on caecal circular smooth muscle cells of guinea pig via both CCK-A and CCK-B/gastrin receptors

This study was designed to investigate the participation of cholecystokinin(CCK)-A and/or CCK-B/gastrin receptors in CCK-8-induced contraction of guinea pig caecal circular smooth muscle cells, using a novel selective CCK-A receptor antagonist, (S)-N-[1-(2-fluorophenyl)-3,4,6,7-tetrahydro-4-oxo-pyrrolo-[3,2,1-jk] [1,4]benzodiazepine-3-yl]-1H-indole-2-carboxamide (FK480), and a novel selective CCK-B/gastrin receptor antagonist, (R)-1-[2,3-dihydro-1-(2'-methylphenacyl)-2-oxo-5-phenyl-1H-1, 4-benzodiazepine-3-yl]-3-(3-methylphenyl)urea (YM022). Concentration-response curves for the contractile effect of CCK-8 alone and in the presence of 0.1nM FK480, 0.1 nM YM022, or a combination of 0.1 nM FK480 and 0.1 nM YM022 on isolated smooth muscle cells were determined. In addition, the inhibitory effects of various concentrations of FK480 or YM022 on 1 nM CCK-8-induced contraction were examined. At a concentration of 0.1 nM, both FK480 and YM022 shifted the concentration-response curve for CCK-8 to the right (about 100 times) with the same potency. In addition, a concentration-response curve for a combination of 0.1 nM FK480 and 0.1 nM YM022 was shifted to the right (about 100 times) of the curves for 0.1 nM FK480 alone or 0.1 nM YM022 alone. Both antagonists inhibited 1 nM CCK-8-induced contraction of caecal circular smooth muscle cells in a concentration-dependent manner, with the similar inhibitory potency. A significant inhibition was obtained at a concentration as low as 0.1 nM FK480 and 0.1 nM YM022. This study strongly suggested the presence of both CCK-A and CCK-B/gastrin receptors in caecal circular smooth muscle cells of guinea pig, and that the contractile effect of CCK-8 on these cells was mediated via both of these receptors.