Adolescent ; Child ; Female ; Ghrelin ; blood ; Glucose ; pharmacology ; Humans ; Male ; Obesity ; blood ; Time Factors

OBJECTIVETo investigate the effect of the expression of ghrelin receptors on the postoperative small intestine dysmotility in rat models.

METHODSThe effect of different concentrations of ghrelin (0, 0.01, 0.1, 0.5, 1.0 μmol/L) on the contraction of smooth muscle strips of rat small intestine in the presence or absence of carbachol was observed in vitro. End-to-side anastomosis was performed in the study group and sham controls were used. The expression of ghrelin receptors(GHS-R1a) in small intestine muscle layers was detected by immunohistochemistry and Western blot.

RESULTSIn vitro, ghrelin enhanced the contraction of smooth muscle strips in the presence of carbachol, and the differences in contraction induced by different concentrations of ghrelin(0.1, 0.5, 1.0 μmol/L) were statistically significant [(223±18)%, (245±22)%, (264±25)%, P<0.01]. Immunohistochemistry study showed that GHS-R1a mainly located in the muscular layer of the bowel wall. The expression of GHS-R1a in the circular and longitudinal muscle was significantly weaker than that in the control group. The expression of ghrelin receptors after surgery was down-regulated in the study group, which was lower than that in the control group(0.51±0.02 vs. 0.71±0.01, P<0.01).

CONCLUSIONDown regulation of ghrelin receptors in small intestine muscle layers may contribute to the occurrence of small intestine dysmotility after intestinal surgery.

Animals ; Down-Regulation ; Gastrointestinal Motility ; drug effects ; physiology ; Ghrelin ; pharmacology ; Intestine, Small ; drug effects ; metabolism ; physiology ; surgery ; Male ; Postoperative Period ; Rats ; Rats, Sprague-Dawley ; Receptors, Ghrelin ; metabolism

OBJECTIVETo investigate the effect and mechanism of ghrelin and its synthetic peptide GHRP-6 on gastric motor in mice.

METHODSIn vivo, the dose-dependent effects of ghrelin (20,50,100,200 mug/kg) and GHRP-6 (20,50,100,200 mug/kg) on gastric emptying were measured by intragastric application of phenol red test which was adapted for use in mice. The effects of atropine, NG-nitro-L-arginine methyl ester (L-NAME), and D-Lys(3)-GHRP-6 (GHS-R antagonist) on the gastric motor induced by ghrelin and GHRP-6 (100 mug/kg) were also investigated. In vitro, the effects of ghrelin (0.01,0.1,1.0,10.0 mumol/L) and GHRP-6 (0.01,0.1,1.0,10.0 mumol/L) on spontaneous contraction of mice fundic muscle strips were studied as well.

RESULTSBoth ghrelin (50,100,200 mug/kg) and GHRP-6 (50,100,200 mug/kg) significantly accelerated gastric emptying (P<0.05), but they failed to accelerate gastric emptying in the presence of atropine, L-NAME and D-Lys(3)-GHRP-6 (P<0.05). Ghrelin (0.1, 1.0, 10.0 mumol/L) and GHRP-6 (0.1, 1.0, 10.0 mumol/L) induced significant contraction of fundic muscle strips in concentration-dependent manner (P<0.05), which could be blocked by tetrodotoxin.

CONCLUSIONGhrelin and its synthetic peptide GHRP-6 accelerate gastric emptying perhaps by activating GHS-R of cholinergic excitatory pathways and nitrergic nervous pathways in the enteric nervous system.

Animals ; Female ; Gastric Emptying ; drug effects ; Ghrelin ; pharmacology ; Male ; Mice ; Mice, Inbred C57BL ; Oligopeptides ; pharmacology ; Stomach ; drug effects ; physiology

OBJECTIVETo investigate the effect of growth hormone secretagogue(ghrelin) on the contraction and relaxation of small intestinal smooth muscle in rats and its mechanism.

METHODSTwenty-four vagotomized rats were injected intraperitoneally with different concentrations of ghrelin (0, 20, 40, 80 μg/kg). The small intestinal transit were observed. The effect of ghrelin(0.01, 0.1, 0.5, 1.0 μmol/L) on the contraction and relaxation of rat small intestinal smooth muscle strips was observed in vitro in the presence of carbachol(50 nmol/L), the locations of ghrelin receptors(GHS-R1a) on different cells in small intestinal muscle layers were detected by immunofluorescence.

RESULTSWith the increase of concentrations, ghrelin elevated the percentage of small intestinal transit[(25.4±1.0)%, (33.7±1.9)%, (39.3±2.4)%, (44.7±2.1)%] in a dose-dependent manner, and the differences were statistically significant among groups(P<0.05). Ghrelin could also enhance the contraction [(67.0±2.4)%,(149.5±3.3)%, (187.1±4.7)%, (213.5±3.4)%] and relaxation[(35.3±1.1)%, (62.9±3.8)%, (79.6±2.7)%, (94.6±2.2)%] of smooth muscle strips mediated by Cch in a dose-dependent manner, and the differences were statistically significant among groups(P<0.05). Immunofluorescence revealed that ghrelin receptors mainly located on membrane of the nerve cells in the muscle layers, while no receptors were observed on membrane of the smooth muscle cells.

CONCLUSIONGhrelin may enhance the effect of the contraction and relaxation of the rat small intestinal smooth muscle mediated by cholinergic neurotransmitters by activating the nerve cells in the enteric plexus.

Animals ; Gastrointestinal Motility ; Ghrelin ; pharmacology ; Intestine, Small ; drug effects ; physiology ; Male ; Muscle Contraction ; drug effects ; physiology ; Muscle, Smooth ; drug effects ; physiology ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo study the therapeutic mechanism of Zhizhu Pill (ZP) for treating functional dyspepsia (FD) rats.

METHODSTotally 30 ten-day-old male rats were randomly divided into the normal control group (n =10) and the model group (n = 20). The FD rat model was induced using gastric administration of 0.1% iodoacetamide (IA) combined tail clamping. The model was evaluated when rats were 8-week old. Successfully modeled rats were randomly divided into the model group (n = 10) and the ZP group (n = 10). Rats in the normal group and the model group were administered with normal saline by gastrogavage, while those in the ZP group were administered with ZP Decoction (2 mL/100 g) by gastrogavage. All medication lasted for 7 successive days. The contractile activity in in vitro longitudinal gastric muscle was recorded using Power Lab biological signal collecting system. The expression of growth hormone secretagogue receptor (GHSR) in stomach of FD rats was detected using Western blot and immunohistochemistry (IHC).

RESULTSCompared with the normal group, average frequencies of gastric contraction and changing rates of amplitude obviously decreased in the model group (P < 0.05). Results of Western blot and IHC showed that the expression of GHSR decreased in the model group (P < 0.01). Compared with the model group, average frequencies of gastric contraction and changing rates of amplitude obviously increased in the ZP group (P < 0.05). Results of Western blot and IHC showed that the expression of GHSR increased in the ZP group (P < 0.01).

CONCLUSIONZP could promote the gastric motility in FD rats induced by gastric administration of IA combined tail clamping, and its mechanism might be related to up-regulating GHSR protein level.

Animals ; Drugs, Chinese Herbal ; pharmacology ; Dyspepsia ; drug therapy ; Gastrointestinal Motility ; Male ; Muscle Contraction ; drug effects ; Muscle, Smooth ; drug effects ; metabolism ; Random Allocation ; Rats ; Receptors, Ghrelin ; metabolism

OBJECTIVETo investigate the effect of ghrelin on duodenal migrating myoelectric complex (MMC) in rats with chronic renal failure (CRF).

METHODSThirty healthy male SD rats were randomly assigned into sham-operated group (n=6) and CRF group (n=24), and the latter group was divided into 4 subgroups according to ghrelin doses administered with or without pretreatment with the receptor antagonist D-Lys(3)-GHRP-6. After a 18-h fasting, the rats with or without pretreatment with D-Lys(3)-GHRP-6 were given subcutaneous injections of ghrelin at different doses to observe the changes in duodenal MMC recorded using a multi lead physiological recording system.

RESULTSGhrelin significantly increased the MMC cycle duration and dose-dependently enhanced the frequency, amplitude and percentage of phase III MMC cycle. This effect was inhibited by the pretreatment with ghrelin receptor antagonist D-Lys(3)-GHRP-6.

CONCLUSIONGhrelin can promote gastrointestinal motilities of rats with CRF, and the receptor of ghrelin can regulate the activity of MMC.

Animals ; Duodenum ; drug effects ; Gastrointestinal Motility ; drug effects ; Ghrelin ; pharmacology ; Kidney Failure, Chronic ; physiopathology ; Male ; Myoelectric Complex, Migrating ; Rats ; Rats, Sprague-Dawley

OBJECTIVE: To explore the effect of ghrelin on the duodenal myoelectrical activity during the feeding state and the fasting state in rats. METHODS: One pair of bipolar silver electrodes were chronically implanted in the duodenal serosa of rats for electromyography. The myoelectrical activity was recorded when ghrelin was injected intravenously into rats during the feeding state or the fasting state. Some rats were pretreated with atropine, phentolamine, propranolol, L-arginine, and (D-Lys3)GHRP-6 respectively to explore the mechanism of ghrelin. RESULTS: Duodenal migrating myoelectrical complex (MMC) could be induced by ghrelin in the feeding state. Ghrelin could shorten the length of duodenal MMC cycle and increase the amplitude and frequency of phase III during the fasting state. The percentage of phase III in the MMC cycle did not change. These effects were inhibited by atropine and L-arginine (D-Lys3)GHRP-6, but not by propranolol and phentolamine. CONCLUSION Ghrelin seems to be closely related to the duodenal motility. The excitatory effect of ghrelin on duodenal MMC might rely on the cholinergic pathway, and have a close relationship with NO. The receptor of ghrelin can regulate its activity.
Animals ; Duodenum ; drug effects ; physiology ; Electromyography ; Female ; Gastrointestinal Motility ; drug effects ; Ghrelin ; pharmacology ; Male ; Muscle, Smooth ; physiology ; Myoelectric Complex, Migrating ; drug effects ; Random Allocation ; Rats ; Rats, Sprague-Dawley

OBJECTIVE: To investigate the influence of electroacupuncture (EA) on ghrelin and the phosphoinositide 3-kinase/protein kinase B/endothelial nitric oxide synthase (PI3K/Akt/eNOS) signaling pathway in spontaneously hypertensive rats (SHRs). METHODS: Eight Wistar-Kyoto rats were used as the healthy blood pressure (BP) control (normal group), and 32 SHRs were randomized into model group, EA group, EA plus ghrelin group (EA + G group), and EA plus PF04628935 group (a potent ghrelin receptor blocker; EA + P group) using a random number table. Rats in the normal group and model group did not receive treatment, but were immobilized for 20 min per day, 5 times a week, for 4 continuous weeks. SHRs in the EA group, EA + G group and EA + P group were immobilized and given EA treatment in 20 min sessions, 5 times per week, for 4 weeks. Additionally, 1 h before EA, SHRs in the EA + G group and EA + P group were intraperitoneally injected with ghrelin or PF04628935, respectively, for 4 weeks. The tail-cuff method was used to measure BP. After the 4-week intervention, the rats were sacrificed by cervical dislocation, and pathological morphology of the abdominal aorta was observed using hematoxylin-eosin (HE) staining. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of ghrelin, nitric oxide (NO), endothelin-1 (ET-1) and thromboxane A2 (TXA2) in the serum. Isolated thoracic aortic ring experiment was performed to evaluate vasorelaxation. Western blot was used to measure the expression of PI3K, Akt, phosphorylated Akt (p-Akt) and eNOS proteins in the abdominal aorta. Further, quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to measure the relative levels of mRNA expression for PI3K, Akt and eNOS in the abdominal aorta. RESULTS: EA significantly reduced the systolic BP (SBP) and diastolic BP (DBP) (P < 0.05). HE staining showed that EA improved the morphology of the vascular endothelium to some extent. Results of ELISA indicated that higher concentrations of ghrelin and NO, and lower concentrations of ET-1 and TXA2 were presented in the EA group (P < 0.05). The isolated thoracic aortic ring experiment demonstrated that the vasodilation capacity of the thoracic aorta increased in the EA group. Results of Western blot and qRT-PCR showed that EA increased the abundance of PI3K, p-Akt/Akt and eNOS proteins, as well as expression levels of PI3K, Akt and eNOS mRNAs (P < 0.05). In the EA + G group, SBP and DBP decreased (P < 0.05), ghrelin concentrations increased (P < 0.05), and the concentrations of ET-1 and TXA2 decreased (P < 0.05), relative to the EA group. In addition, the levels of PI3K and eNOS proteins, the p-Akt/Akt ratio, and the expression of PI3K, Akt and eNOS mRNAs increased significantly in the EA + G group (P < 0.05), while PF04628935 reversed these effects. CONCLUSION EA effectively reduced BP and protected the vascular endothelium, and these effects may be linked to promoting the release of ghrelin and activation of the PI3K/Akt/eNOS signaling pathway.
Animals ; Electroacupuncture ; Ghrelin/pharmacology* ; Nitric Oxide/metabolism* ; Nitric Oxide Synthase Type III/pharmacology* ; Phosphatidylinositol 3-Kinase/pharmacology* ; Phosphatidylinositol 3-Kinases/metabolism* ; Proto-Oncogene Proteins c-akt/pharmacology* ; Rats ; Rats, Inbred SHR ; Rats, Inbred WKY ; Signal Transduction

OBJECTIVETo explore the effects of ghrelin on learning and memory abilities and expressions of DKK-1 and β-catenin in the hippocampus of diabetic rats.

METHODSSixty male SD rats were randomly assigned into 4 groups, namely the control group, diabetic group, ghrelin-treated diabetic group (DM1 group), and ghrelin- and D-lys3-GHRP-6 (a GHSR-1a receptor antagonist)-treated diabetic group (DM2 group). Diabetic rat models were established by a single intraperitoneal injection of streptozotocin (65 mg/kg). The learning and memory abilities of the rats were assessed with Morris water maze (MWM) test. The ultrastructure of the hippocampal CA1 area of the rats were observed with electron microscopy. Serum levels of DKK-1 were examined by ELISA, and the expressions of DKK-1 and β-catenin in the hippocampus were examined by quantitative real-time PCR and Western blotting.

RESULTSCompared with the control group, the diabetic rats exhibited significantly impaired learning and memory abilities (P<0.05), increased expression of DKK-1 and lowered β-catenin expression in the hippocampus (P<0.05), significant ultrastructural injuries and disordered arrangement of neurons with the nuclear pycnosis in the hippocampal CA1 area. Ghrelin treatment of the diabetic rats obviously improved their learning and memory abilities (P<0.05), reduced DKK-1 and increased β-catenin expressions (P<0.05), ameliorated ultrastructural damages in the hippocampal CA1 area and restored normal neuronal alignment with clear cell layers. Such effects of ghrelin were antagonized by treatment with D-lys3-GHRP-6 in the diabetic rats.

CONCLUSIONGhrelin can alleviate learning and memory dysfunction in diabetic rats possibly by down-regulating the expressions of DKK-1 and activating the WNT signaling pathways.

Animals ; CA1 Region, Hippocampal ; cytology ; metabolism ; pathology ; Cognition ; Diabetes Mellitus, Experimental ; metabolism ; Ghrelin ; pharmacology ; Intercellular Signaling Peptides and Proteins ; metabolism ; Learning ; Male ; Memory ; Neurons ; pathology ; Oligopeptides ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Real-Time Polymerase Chain Reaction ; Streptozocin ; beta Catenin ; metabolism

Body Height ; Child ; Female ; Ghrelin ; pharmacology ; Growth Disorders ; physiopathology ; Growth Hormone-Releasing Hormone ; pharmacology ; Human Growth Hormone ; blood ; physiology ; urine ; Humans ; Insulin-Like Growth Factor Binding Protein 3 ; blood ; Insulin-Like Growth Factor I ; physiology ; Male