Release of cholecystokinin from rat cerebral cortex in vivo: role of GABA and glutamate receptor systems

Using cortical cups in chloralose-urethanized rats, the in vivo release of cholecystokinin-like immunoreactivity (CCK-LI) from cerebral cortex was examined. Resting levels of cholecystokinin-like immunoreactivity ranged from 20 to 30 pg/20 min sample. The addition of potassium (40 mM) in excess, resulted in a highly significant elevation in the levels of CCK-LI in the cortical superfusate. Deletion of calcium and the substitution of cobalt (10 mM), resulted in a significant reduction in both resting release and the release otherwise evoked by the addition of potassium. Focal electrical stimulation of the cortex (20 Hz), resulted in a significant (1.9 +/- 0.2-fold, n = 8) increase in the levels of CCK-LI. The addition of glutamate (10(-6)-10(-4) M) of kainic acid (10(-8)-10(-6) M), also resulted in significant elevations in the levels of CCK-LI. The co-administration of a putative glutamate receptor antagonist, kynurenic acid (10(-4) M) resulted in a significant reduction in the levels of release otherwise evoked by the addition of glutamate, but not by electrical stimulation. The addition of GABA (10(-5)-10(-3) M) resulted in a dose-dependent decrease in the resting release of CCK-LI, and the release evoked by glutamate. Picrotoxin (10(-6)-10(-4) M), resulted in a highly significant increase in the levels of CCK-LI in the cortical effluent. These results are consistent with a tonic GABAergic inhibition of CCK-releasing neurons. The treatment of the animal with diazepam (30 mg/kg, i.p.) also resulted in a significant reduction in resting release and the release otherwise evoked by focal cortical stimulation.     

胆汁胆固醇对胆囊收缩素受体表达的影响

目的：探讨胆汁胆固醇对胆囊收缩素受体（CCK－R）表达的影响。方法 采用放射免疫分析法和受体放射配基结合法检测对照组、高胆固醇组、自然恢复组及治疗组豚鼠门静脉血CCK水平、胆囊CCK－R的最大结合容量（Bmax）和亲和力（Kd），同时观察空腹胆囊体积（FV）、胆囊胆汁量（FB）和餐后胆囊体积（RV）、胆囊胆汁量（RB）及胆囊收缩率（E％）、胆汁胆固醇浓度的变化。结果 与对照组比较，高胆固醇组豚鼠FV、FB增大（P＜0.05），RV、RB也增大，胆囊收缩率下降（P＜0.01），胆汁胆固醇浓度升高（P＜0.05），门静脉血CCK水平及CCK－R的Kd无改变，而CCK－R的Bmax下降（P＜0.01）；治疗组上述各项指标正常。结论 胆汁中的高胆固醇通过下调胆囊CCK－R表达而导致胆囊收缩功能障碍，降低胆汁高胆固醇浓度可以促进胆囊动力功能的恢复。     

Illness-induced hyperalgesia is mediated by spinal neuropeptides and excitatory amino acids

The spinal cord dorsal horn contains neural mechanisms which can greatly facilitate pain. We have recently shown that ‘illness’-inducing agents, such as intraperitoneally administered lipopolysaccharide (LPS; bacterial endotoxin), can produce prolonged hyperalgesia. This hyperalgesic state is mediated at the level of the spinal cord via activation of the NMDA-nitric oxide cascade. However, prolonged neuronal depolarization is required before such a cascade can occur. The present series of experiments were aimed at identifying spinal neurotransmitters which might be responsible for creating such a depolarized state. These studies show that LPS hyperalgesia is mediated at the level of the spinal cord by substance P, cholecystokinin and excitatory amino acids acting at non-NMDA sites. No apparent role for serotonin or kappa opiate receptors was found.     

Baclofen Pretreatment Attenuates the Suppressant Effect of Intraperitoneal Administration of Cholecystokinin (CCK) on Food Intake in Rats

The aim of this study was to investigate whether pretreatment with the GABAB receptor agonist baclofen could prevent the inhibitory effect of systemically administered cholecystokinin (CCK) on food intake in rats. Baclofen (2 mg/kg, SC) administered 60 min prior to IP injection of CCK (5 μg/kg) significantly attenuated the suppressant effect of the peptide on feeding in nondeprived rats (Experiment 1) and rats that had been deprived of food for 22 h (Experiment 2). Baclofen had no significant effects on food intake when administered alone. The results suggest that the inhibitory effect of exogenous peripheral CCK on food intake may be dependent on an interaction with a GABAB-receptor mediated mechanism. Copyright © 1996 Elsevier Science Inc.     

大鼠孤束核含酪氨酸羟化酶、神经降压素和胆囊收缩素样神经元向伏核的投射—HRP和免疫细胞化学双重标记法的研究

本文应用HRP顺、逆行追踪法结合免疫细胞化学双重标记法,对大鼠孤束核向伏核的投射进行了研究。主要结果如下:1.WGA-HRP注入孤束核尾侧段,在伏核后部的腹、内侧区,出现较密集的标记纤维、终末和标记细胞;将HRP注入伏核后部的腹、内侧区,在孤束核尾侧段(主要在连合核和内侧亚核)出现大量的顺、逆行标记,以同侧为主。2.HRP注射到伏核并结合免疫细胞化学反应,在孤束核尾侧段发现HRP-TH,HRP-NT、HRP-CCK双重标记细胞。HRP-TH的数目最多,其次是HRP-NT双标细胞,HRP-CCK双标细胞最少。     

Prolyl-leucyl-glycinamide shares some effects with oxytocin but decreases oxytocin levels

Oxytocin treatment in rats induces long-lasting antistress and growth promoting effects. This study investigated whether prolyl-leucyl-glycinamide (PLG) (the c-terminal tripeptide of oxytocin) or tocinoic acid (the ring structure of oxytocin) could induce some of these effects in male rats. For this purpose, PLG (2 or 10 mg/kg, s.c.) or tocinoic acid (1 mg/kg, s.c.) was administered to rats once a day for 3 or 5 days. Blood pressure, heart rate, spontaneous motor activity, nociceptive thresholds, and the survival of ischaemic musculocutaneous flaps were measured. In addition, endogenous oxytocin levels and plasma levels of some hormones known to be influenced by oxytocin were determined. PLG (2 mg/kg, s.c., but not 10 mg/kg, s.c.) decreased diastolic blood pressure (p<0.05) and locomotor activity (p<0.05). PLG (10 mg/kg, s.c.) decreased gastrin (p<0.05) and endogenous oxytocin levels in plasma (p<0.01). Tocinoic acid decreased locomotor activity (p<0.05), but did not affect any of the other parameters measured. In conclusion, this study showed that both PLG and tocinoic acid decrease locomotor activity. In addition, PLG also induced some other effects similar to those induced by oxytocin treatment but when administered in high doses it decreased oxytocin levels.     

Fat in the intestine as a regulator of appetite--role of CCK

The present review summarizes the appetite-suppressing effects of intestinal fat in the regulation of food intake in humans, with a special focus on the role of cholecystokinin (CCK). Current evidence supports a role for intestinal fat (especially long-chain free fatty acids) acting via the peptide CCK as a physiological satiety pathway. The regulation of satiety is, however, complex and it is not surprising that multiple control systems exist. It is interesting to note that nutrients, such as hydrolysis products of fat in the small intestine, stimulate the release of satiety peptides, such as CCK or PYY, that serve as satiety signals. CCK, released from the gastrointestinal tract by the local action of digested food, exerts various functions: stimulation of gallbladder contraction and exocrine pancreatic secretion, inhibition of gastric emptying, and inhibition of appetite. CCK functions therefore (1) as a positive feedback signal to stimulate digestive processes and (2) as negative feedback signal to limit the amount of food consumed during an individual meal.     

Gastric capacity, test meal intake, and appetitive hormones in binge eating disorder

Binge eating disorder (BED), characterized by ingestion of very large meals without purging afterwards, is found in a subset of obese individuals. We showed previously that stomach capacity is greater in obese than in lean subjects, and in this study, we investigated capacity in obese individuals with BED. We also determined ad-libitum intake of a test meal until extremely full. Furthermore, we measured various appetitive hormones (insulin, leptin, glucagon, CCK, ghrelin) and glucose before a fixed meal and for 120 min afterwards. An acetaminophen tracer was used to assess gastric emptying rate. We compared three groups of overweight women: 11 BED, 13 BE (subthreshold BED), and 13 non-binge-eating normals. The BED individuals had the largest stomach capacity as assessed by either maximum volume tolerated (P=.05) or by gastric compliance to pressure (P=.02) using an intragastric balloon. Although test meal intake did not differ between groups, it correlated (P=.03) with gastric capacity. The BED group showed a tendency (P=.06) to have greater area under the curve (AUC) and had higher values at 5 and 60 min (P<.05) for insulin compared to normals. Moreover, the BED subjects had lower ghrelin baselines premeal, and lower AUC for ghrelin, which then declined less postmeal than for the normals (P<.05). None of the other blood values differed, including glucose, leptin glucagon, and CCK, as well as acetaminophen, reflecting gastric emptying. The lower ghrelin in BED, although contrary to what was expected, is consistent with lower ghrelin in obesity, and suggests down-regulation of ghrelin by overeating. The lack of differences in CCK is consistent with the lack of differences in gastric emptying rate, given that CCK is released when nutrients reach the intestine. The results show that BED subjects have a large gastric capacity as well as abnormalities in meal-related ghrelin and insulin patterns that may be factors in binge eating.     

Secretagogue effects on intracellular calcium in pancreatic duct cells

Regulation of intracellular free calcium ([Ca²⁺]_i) in single epithelial duct cells of isolated rat and guinea pig pancreatic interlobular ducts by secretin, carbachol and cholecystokinin was studied by microspectrofluorometry using the Ca²⁺-sensitive, fluorescent probe Fura-2. Rat and guinea pig duct cells exhibited mean resting [Ca²⁺]_i of 84 nM and 61 nM, respectively, which increased by 50%–100% in response to carbachol stimulation, thus demonstrating the presence of physiologically responsive cholinergic receptors in pancreatic ducts of both species. The carbachol-induced increase in [Ca²⁺]_i involved both mobilization of Ca²⁺ from intracellular stores and stimulation of influx of extracellular Ca²⁺. In contrast, neither cholecystokinin nor secretin showed reproducible or sizeable increses in [Ca²⁺]_i. Both rat and guinea pig duct cells showed considerable resting Ca²⁺ permeability. Lowering or raising the extracellular [Ca²⁺]_i led, respectively, to a decrease or increase in the resting [Ca²⁺]_i. Application of Mn²⁺ resulted in a quenching of the fluorescence signal indicating its entry into the cell. The resting Ca²⁺ and Mn²⁺ permeability could be blocked by La³⁺ suggesting that it is mediated by a Ca²⁺ channel.     

Neuropeptide gene expression in brain is differentially regulated by midbrain dopamine neurons

Summary In situ hybridization was used to study the expression of prepro-neuropeptide Y (NPY), preprosomatostatin (SOM), preprotachykinin (PPT) and preprocholecystokinin (CCK) mRNA in caudate-putamen and frontoparietal cortex of rat brain with unilateral lesion of midbrain dopamine neurons. Neurons expressing NPY and SOM mRNA showed a similar distribution and the expression of both NPY and SOM appears to be regulated by dopamine in a similar fashion. Following a dopamine deafferentation, the numerical density of both NPY and SOM mRNA producing neurons almost doubled in the lesioned caudate-putamen with no change in the average grain density over positive neurons. Hence, in the intact caudate-putamen dopamine appears to suppress expression of these two neuropeptide genes leading to an activation of both NPY and SOM mRNA expression in many non- or low-expressing neurons when the level of dopamine is decreased. In the fronto-parietal cortex, on the other hand, dopamine appears to stimulate NPY and SOM gene expression. Thus, in the absence of dopamine about half of the NPY positive neurons disappeared. However, for SOM the number of positive neurons did not change, but rather most positive neurons appeared to have down-regulated their SOM mRNA expression. No evidence was found for a change in CCK mRNA expression by the dopamine deafferentation, while PPT mRNA expression decreased in the deafferented caudate-putamen. Consequently, dopamine exerts dissimilar effects on the expression of different neuropeptide genes, that in turn do not respond in the same way in different brain regions.