Y-27632 inhibits gastric motility in conscious rats

Y-27632, a highly selective inhibitor of p160ROCK, desensitizes the smooth muscle to Ca2+ and inhibits smooth muscle contraction. While this drug has the potential to become a novel drug for hypertension, it might also affect other smooth muscle, including that of gastrointestinal tract. We studied the effects of Y-27632 on gastric contractions in conscious rats. Strain gauge force transducers were sutured onto the serosal side of the gastric antrum and contractions were recorded before and after the intravenous injection of Y-27632. Doses of 1.0 mg/kg to 10 mg/kg significantly decreased contraction amplitude and the motility index in a dose dependent manner. With 10 mg/kg, the mean amplitude was decreased by up to 69 +/- 14% and the motility index by up to 81 +/- 7%. The change occurred immediately after drug infusion and lasted for 3.5h. Contraction frequency showed only a slight decrease. No signs of bowel obstruction were observed. These results indicate that Rho-mediated Ca sensitization has a role in the physiologic contractions of gastric smooth muscle in rats. Y-27632 is useful to investigate the physiology of gastrointestinal motility.     

Regulation of gastric motility at simulated high altitude in conscious rats.

The aim of the present study was to examine the effects of acute exposure to hypobaric hypoxia on gastric and colonic motilities. Wistar rats, which were instrumented chronically with strain gauge force transducer to measure gastric and colonic motilities, were exposed acutely to hypobaric hypoxia [0.5 atmosphere absolute (ATA, 380 Torr)] over 1 h. In a separate group, the gastric branches of the vagal nerves were cut and underwent the same experimental protocol. Each contraction wave of the stomach and colon was analyzed into frequency and area under the curves, which were then averaged every 10 min. Acute exposure to 0.5 ATA resulted in significant (P < 0.05) decreases in frequency and area of gastric contraction wave by 0.5 +/- 0.1 cycles/min and 64.6 +/- 4.0%, respectively. Gastric vagotomy abolished completely the suppression in the area observed in the intact rats during the 0.5-ATA exposures. Colonic motility increased significantly only at the start and end of exposure to 0.5 ATA and sham exposure [1 ATA (760 Torr), time control] in both intact and vagotomized rats. These data suggest that the acute suppression of the area of the gastric contraction wave that occurred during 0.5-ATA exposure is likely to be mediated by the vagal nerve.     

Impacts of peripheral obestatin on colonic motility and secretion in conscious fed rats

Obestatin, a novel putative 23-amino acid peptide, was found to be derived from a mammalian preproghrelin gene by using a bioinformatics approach. Although the effects of obestatin on food intake and upper gut motility remain controversial, no studies have been carried out to explore its influence on lower gut motility and secretion. We investigated the impacts of intravenous (IV) injection of obestatin on rat colonic motor and secretory functions. Colonic transit time, fecal pellet output, and fecal content were measured in freely fed, conscious rats, which were chronically implanted with IV and colonic catheters. To test the validity of this animal model, human/rat corticotropin-releasing factor (h/rCRF) served as a stimulatory inducer of colonic motility and secretion. IV injection of obestatin (45, 100, and 300nmol/kg) did not affect the colonic transit time, whereas IV injection of h/rCRF (30nmol/kg) effectively accelerated colonic transit time. IV obestatin, in every dose we tested, also did not modify fecal pellet output, frequency of watery diarrhea, total fecal weight, fecal dried solid weight, or fecal fluid weight in the first hour after injection. On the other hand, IV injection of h/rCRF significantly enhanced fecal pellet output, as well as increased the frequency of watery diarrhea, total fecal weight, fecal dried solid weight, and fecal fluid weight during the first hour after injection compared with IV saline controls. In conclusion, peripheral obestatin administration has no impact on colonic motility and secretion in conscious fed rats.     

Dual effect of bombesin and gastrin releasing peptide on gastric emptying in conscious cats

The effect of bombesin (BBS) and gastrin releasing peptide (GRP) on gastric emptying was studied in conscious cats. This effect was measured simultaneously with antral motility. Acid and pepsin secretions as well as blood hormonal peptide release were additionally measured. A dual effect was observed. First, BBS and GRP slowed gastric emptying of liquids, while antral motility was decreased, then after 60 minutes of continuous intravenous infusion, antral motility returned to basal values and gastric emptying effect reversed. The mechanism of this peculiar action is independent of gastrin, pancreatic polypeptide, somatostatin and motilin release and most probably connected with a cholinergic stimulation induced by the peptides, the late predominance of which counterbalances the inhibitory effect of bombesin-like peptides on antral motility.     

Modulation of gastric acid secretion by adenosine in conscious rats

Basal (nonstimulated) gastric acid output was determined in conscious rats fitted with indwelling gastric cannulae. The adenosine deaminase resistant analog of adenosine, R-phenylisopropyladenosine, elevated intraluminal pH beyond 7.0 and decreased gastric acid secretion when given at doses of 0.10 or 1.0 mg/kg, while S-phenylisopropyladenosine at similar doses did not affect either gastric acid output or pH. The potent adenosine receptor antagonist, 8-phenyltheophylline, given at doses of 0.1, 1.0, and 2.5 mg/kg augmented gastric acid output and, at doses of 0.01, 0.1, 1.0, and 2.5 mg/kg, blocked the acid-reducing effect of R-phenylisopropyladenosine (0.1 mg/kg). These data suggest that adenosine systems may be important regulators of gastric function.     

糖尿病大鼠弓状核-海马肥胖抑素通路构成及对胃运动和胃排空的影响

目的: 探究糖尿病大鼠弓状核(ARC)-海马肥胖抑素(obestatin)神经通路构成,以及该通路对大鼠胃运动、胃排空的影响。方法: 健康雄性Wistar大鼠采用果糖溶液诱导胰岛素抵抗加腹腔注射链脲佐菌素的方法制备糖尿病模型,造模之后,随机分为5组:对照组(NS组)、0.1、1和10 pmol obestatin组、obestatin+NBI27914组,每组7只;各组通过置管分别向海马内注射0.5 μl 生理盐水(NS)、obestatin(0.1 pmol、1 pmol、10 pmol)和混合液(10 pmol obestatin + 60 pmol NBI27914),给药后立即记录大鼠胃运动,15 min后进行胃排空研究;通过荧光金(FG)逆行追踪及免疫组化方法比较正常及糖尿病大鼠ARC-海马obestatin神经通路构及ARC obestatin mRNA表达的异同。结果: 与正常大鼠相比,糖尿病大鼠ARC FG/obestatin双标神经元数目显著减少(P＜0.05),ARC obestatin mRNA表达量显著下降(P＜0.05);obestatin各组可剂量依赖性的抑制大鼠胃运动及胃排空(P＜0.05~0.01),obestatin的这些效应可被促肾上腺皮质激素受体1(CRFR1)阻断剂NBI27914部分阻断(P＜0.05);obestatin对糖尿病大鼠胃运动和胃排空的抑制效应显著减弱(P＜0.05)。结论: ARC-海马之间存在obestatin神经和功能通路,参与糖尿病大鼠胃运动及胃排空调控,且CRFR1信号通路参与该过程。该通路功能的减弱可能参与了糖尿病早期胃动力紊乱的发病。     

Ghrelin stimulates gastric acid secretion and motility in rats

Ghrelin, a novel growth-hormone-releasing peptide, was discovered in rat and human stomach tissues. However, its physiological and pharmacological actions in the gastric function remain to be determined. Therefore, we studied the effects of rat ghrelin on gastric functions in urethane-anesthetized rats. Intravenous administrations of rat ghrelin at 0.8 to 20 microgram/kg dose-dependently increased not only gastric acid secretion measured by a lumen-perfused method, but also gastric motility measured by a miniature balloon method. The maximum response in gastric acid secretion was almost equipotent to that of histamine (3 mg/kg, i.v.). Moreover, these actions were abolished by pretreatment with either atropine (1 mg/kg, s.c.) or bilateral cervical vagotomy, but not by a histamine H(2)-receptor antagonist (famotidine, 1 mg/kg, s.c.). These results taken together suggest that ghrelin may play a physiological role in the vagal control of gastric function in rats.     

Spinal effects of oxytocin on uterine motility in anesthetized rats

The rat uterus receives an innervation from the lumbosacral and thoracolumbar segments of the spinal cord. These segments receive descending oxytocinergic projections from the paraventricular nucleus of the hypothalamus. We tested the hypothesis that oxytocin regulates uterine motility through a spinal site of action. Oxytocin was administered in anesthetized female rats either intrathecally at the lumbosacral or thoracolumbar spinal cord levels or intravenously. Uterine activity was revealed by measuring changes of intrauterine pressure using an indwelling balloon placed in one caudal uterine horn. The uterus displayed a spontaneous activity characterized by intrauterine pressure rises, the frequency, amplitude, and duration of which were dependent on the stage of the estrous cycle. Oxytocin delivered at the lumbosacral level affected the frequency (during proestrus, estrus, and diestrus) and amplitude (during proestrus and estrus) of uterine activity. During estrus, oxytocin delivered at the thoracolumbar level affected the frequency, amplitude, and duration of the intrauterine pressure rises. Intravenous oxytocin not only affected intrauterine pressure rises (namely amplitude during proestrus and estrus and frequency and duration during estrus) but also increased the basal tone during estrus. The effects of lumbosacral oxytocin were partly mimicked by the oxytocin agonist [Thr(4),Gly(7)]-oxytocin blocked by the oxytocin receptor antagonist atosiban and by hexamethonium. Arginine vasopressin delivered at the lumbosacral level had no effect. These results support our hypothesis that oxytocin released by descending paraventriculo-spinal pathways and acting on spinal oxytocin receptors modulates the activity of the uterus. This regulation is cycle dependent.     

Effects of acupuncture on vasopressin-induced emesis in conscious dogs

Although acupuncture has a significant clinical benefit, the mechanism of acupuncture remains unclear. Vasopressin, a posterior pituitary hormone, is involved in nausea and vomiting in humans and dogs. To investigate the antiemetic effects of acupuncture on vasopressin-induced emesis, gastroduodenal motor activity and the frequency of retching and vomiting were simultaneously recorded in conscious dogs. In seven dogs, four force transducers were implanted on the serosal surfaces of the gastric body, antrum, pylorus, and duodenum. Gastroduodenal motility was continuously monitored throughout the experiment. Vasopressin was intravenously infused at a dose of 0.1 U x kg(-1) x min(-1) for 20 min. Electroacupuncture (EA, 1-30 Hz) at pericardium-6 (PC6), bladder-21 (BL21), or stomach-36 (ST36) was performed before, during, and after the vasopressin infusion. To investigate whether the opioid pathway is involved in EA-induced antiemetic effects, naloxone (a central and peripheral opioid receptor antagonist) or naloxone methiodide (a peripheral opioid receptor antagonist) was administered before, during, and after EA and vasopressin infusion. Intravenous infusion of vasopressin induced retching and vomiting in all dogs tested. Retrograde peristaltic contractions occurred before the onset of retching and vomiting. EA (10 Hz) at PC6 significantly reduced the number of episodes of retching and vomiting. EA at PC6 also suppressed retrograde peristaltic contractions. In contrast, EA at BL21 or ST36 had no antiemetic effects. The antiemetic effect of EA was abolished by pretreatment with naloxone but not naloxone methiodide. It is suggested that the antiemetic effect of acupuncture is mediated via the central opioid pathway.     

Cardiovascular effects of cocaine in anesthetized and conscious rats

This study examined the cardiovascular and respiratory effects of cocaine and procaine in anesthetized and conscious rats. Intravenous cocaine (0.16-5 mg/Kg) elicited a rapid, dose dependent increase in mean arterial pressure of relatively short duration. In pentobarbital anesthetized (65 mg/Kg, i.p.) animals, the pressor phase was generally followed by a more prolonged depressor phase. These effects on arterial pressure were generally accompanied by a significant tachypnea and at larger doses (2.5 and 5 mg/Kg, i.v.), bradycardia. Procaine (0.31 and 1.25 mg/Kg, i.v.) produced similar cardiovascular and respiratory effects (depressor phase, tachypnea) in pentobarbital anesthetized animals. In conscious-restrained animals, both cocaine and procaine (1.25 mg/kg, i.v.) produced pressor responses. The subsequent depressor response was, however, absent in both cases. The cardiovascular effects of cocaine (0.25-1 mg/Kg, i.v.) in urethane anesthetized (1.25 g/Kg, i.p.) animals were essentially similar to those observed in conscious animals. Procaine (1mg/Kg) did not produce any significant cardiovascular effects in urethane anesthetized animals, but did elicit tachypnea. Reserpine pretreatment (10 mg/Kg, i.p.) did not significantly attenuate the pressor response in urethane anesthetized animals. Phentolamine pretreatment (3 mg/Kg, i.v.) did significantly antagonize the pressor effect in urethane anesthetized animals. These results suggest that: the depressor phase is likely due to a interaction between local anesthetic activity (cocaine and procaine) and barbiturate anesthesia, the cardiovascular effects of cocaine in conscious animals are more similar to those observed in urethane anesthetized rats than in pentobarbital anesthetized rats and the pressor effect in urethane anesthetized rats is apparently due to a reserpine resistant catecholaminergic mechanism.     

Hemodynamic effects of calcitonin gene-related peptide in conscious rats

The cardiovascular effects of calcitonin gene-related peptide (CGRP) were examined in conscious, unrestrained rats. Changes in mean arterial pressure, heart rate and cardiac output were continuously monitored before and after i.v. bolus injection of CGRP (0.1-5 micrograms/kg). Injection of the peptide caused dose-dependent reductions in mean arterial pressure (-24 +/- 4 mmHg), which were accompanied by marked tachycardia. Cardiac output was significantly increased after CGRP but little change was observed in stroke volume. CGRP also reduced total peripheral resistance (-46 +/- 6%). These data indicate that the hypotensive actions of CGRP are mediated through peripheral vasodilation rather than through reductions in cardiac output. Pretreatment with propranolol significantly reduced the tachycardia responses to CGRP from 81 +/- 11 beats/min to 36 +/- 4 beats/min, but did not abolish the increase in heart rate. These data suggest that CGRP produces a tachycardia through reflex increases in cardiac sympathetic tone and through possible direct positive chronotropic effects on the heart.     

Somatic pain sensitivity of conscious rats with chronic gastric ulcers

The aim of the study was to investigate the effect of gastric ulcers on somatic nociception in conscious rats. The formation of kissing gastric ulcers was induced by luminal application of 60% acetic. Somatic pain sensitivity was tested by tail flick latency. Application of acetic acid resulted in gastric ulcer formation, somatic hyperalgesia and the appearance of typical signs of chronic stress (a long-lasting increase of plasma corticosterone level, adrenal gland hypertrophy and thymus gland involution). Natural healing of gastric ulcers was accompanied by restoration of pain sensitivity and attenuation of typical signs of chronic stress. Both natural healing of gastric ulcers and restoration of pain sensitivity were prevented by daily indomethacin administration. The results suggest that the formation of chronic gastric ulcers may trigger somatic hypersensitivity.     

Phytohaemagglutinin inhibits gastric acid but not pepsin secretion in conscious rats

Phytohaemagglutinin (PHA), a kidney bean lectin, is known for its binding capability to the small intestinal surface. There has been no data available, however, on the biological activity of PHA in the stomach. Recent observations indicate that PHA is able to attach to gastric mucosal and parietal cells. Therefore, we examined whether PHA affects gastric acid and pepsin secretion in rats. Rats were surgically prepared with chronic stainless steel gastric cannula and with indwelling polyethylene jugular vein catheter. During experiments, animals were slightly restrained. Gastric acid secretion was collected in 30 min periods. Acid secretion was determined by titration of the collected gastric juice with 0.02 N NaOH to pH 7.0. Pepsin activity was estimated by measuring enzymatic activity. Saline, pentagastrin and histamine were infused intravenously. PHA or bovine serum albumin (BSA) were dissolved in saline and given intragastrically through the gastric cannula. PHA significantly inhibited basal acid secretion. Inhibition of acid output reached 72% during the first collection period following PHA administration when compared, then gradually disappeared. Pentagastrin-stimulated acid secretion was repressed dose-dependently by PHA as well. Maximal inhibition was observed during the first 30 min following application of PHA. Histamine-stimulated acid secretion was inhibited by PHA in a similar manner. Pepsin secretion was not affected by PHA under either basal or stimulated conditions. These results provide evidence that PHA is a potent inhibitor of gastric acid secretion in conscious rats, but it does not affect pepsin output from the stomach.     

卵巢激素调节大鼠胃运动及感觉功能的机制

女性患者在孕期及月经周期的黄体期常有腹痛、腹胀及腹泻等胃肠道功能紊乱的症状.本文探讨雌二醇（estradiol benzoate,EB）和孕酮（progesterone,P4）对卵巢切除大鼠血浆胆囊收缩素（cholecystokinin,CCK）及胃组织内胆囊收缩素受体A（CCKA）、血浆降钙素基因相关肽（calcitonin gene-related peptide,CGRP）及胃组织内其受体表达水平的影响,以期阐明卵巢激素调节胃肠道运动及感觉功能的机制.给予卵巢切除大鼠EB和P4替代治疗,用放射免疫分析法测定血浆CCK、CGRP的浓度,用Western blot法检测胃组织内CCKA受体的表达量,用125I-CGRP放射配体结合分析法测定胃组织内CGRP受体的表达量.EB可以升高血浆CCK的浓度,同时引起胃组织内CCKA受体表达增高.P4对血浆CCK的浓度以及胃组织内CCKA受体的表达无明显影响,但P4可以升高血浆CGRP的浓度,上调胃组织内CGRP受体的活性.EB、P4联合作用升高血浆CCK、CGRP的浓度,增加胃内CCKA、CGRP受体的表达.因此EB通过促进CCK的分泌以及上调胃内CCKA受体的表达,抑制胃排空;而P4可以通过增加CGRP的释放上调胃内CGRP受体的活性,从而增加肠神经系统对外来刺激的敏感性.结果提示,可以利用CCKA、CGRP受体的拈抗剂治疗女性患者中与月经周期有密切关系的胃肠道功能紊乱症状,如腹胀、早饱、腹痛等.     

Electroacupuncture at ST-36 accelerates colonic motility and transit in freely moving conscious rats

Acupuncture is useful for functional bowel diseases, such as constipation and diarrhea. However, the mechanisms of beneficial effects of acupuncture on colonic function have scarcely ever been investigated. We tested the hypothesis that electroacupuncture (EA) at ST-36 stimulates colonic motility and transit via a parasympathetic pathway in conscious rats. Hook-shaped needles were inserted at bilateral ST-36 (lower limb) or BL-21 (back) and electrically stimulated at 10 Hz for 20 min. We also studied c-Fos expression in response to EA at ST-36 in Barrington's nucleus of the pons. EA at ST-36, but not BL-21, significantly increased the amplitude of motility at the distal colon. The calculated motility index of the distal colon increased to 132 +/- 9.9% of basal levels (n = 14, P < 0.05). In contrast, EA at ST-36 had no stimulatory effects in the proximal colon. EA at ST-36 significantly accelerated colonic transit [geometric center (GC) = 6.76 +/- 0.42, n = 9, P < 0.001] compared with EA at BL-21 (GC = 5.23 +/- 0.39, n = 7). The stimulatory effect of EA at ST-36 on colonic motility and transit was abolished by pretreatment with atropine. EA-induced acceleration of colonic transit was also abolished by extrinsic nerve denervation of the distal colon (GC = 4.69 +/- 0.33, n = 6). The number of c-Fos-immunopositive cells at Barrington's nucleus significantly increased in response to EA at ST-36 to 8.1 +/- 1.1 cells/section compared with that of controls (2.4 +/- 0.5 cells/section, n = 3, P < 0.01). It is concluded that EA at ST-36 stimulates distal colonic motility and accelerates colonic transit via a sacral parasympathetic efferent pathway (pelvic nerve). Barrington's nucleus plays an important role in mediating EA-induced distal colonic motility in conscious rats.     

针刺对急性低氧大鼠神经元损伤的保护作用

目的：探讨针刺对急性低氧大鼠神经细胞损伤的保护作用。方法：测定对照组、低氧组、针刺组大鼠脑含水量,脑腺苷A1受体表达水平和观察神经细胞形态学。结果：与低氧组相比,针刺组脑含水量明显降低,神经元无明显的胞浆空染,核固缩;腺苷A1受体表达水平显著增多。结论：针刺具有保护急性低氧对大鼠神经细胞损伤的作用。     

Central cardiovascular effects of mammalian neurohypophyseal peptides in conscious rats

To confirm and extend the results of previous studies which demonstrated central cardiovascular effects of vasopressin in anesthetized rats, we determined blood pressure and heart rate changes for 30 minutes after intracerebroventricular injections of arginine vasopressin, arginine vasotocin and oxytocin in conscious rats. As compared to sham injections, significantly greater increases in either systolic or diastolic blood pressure were noted over the 30 minutes which followed the injection of 0.15, 1.0 or 10.0 nM of either vasopressin or vasotocin. In animals given vasopressin, plasma levels of the peptide were determined. There was a substantial increase in plasma vasopressin only after the highest dose. Overall blood pressure responses to doses of oxytocin as high as 100 nM were not significantly different than sham injections. Heart rate following both vasopressin and vasotocin was increased at 0.15 nM, was initially decreased then increased at 1.0 nM and was substantially decreased after the 10.0 nM dose. There was a significant increase in heart rate at the 10.0 nM and 100 nM doses of oxytocin. Dose response curves for systolic blood pressure and heart rate 20 minutes after injection were similar for vasopressin and vasotocin. We conclude that arginine vasopressin has significant central pressor and tachycardic effects in conscious rats, and it is related, at least in part, to the tail structure of the peptide, which is shared with arginine vasotocin.     

Respiratory and metabolic effects of decreased osmolality in conscious rats

We investigated the respiratory and metabolic effects of decreased osmolality, and the potential roles of angiotensin II (ANG II) and the subfornical organ (SFO) in mediating these effects, in conscious Sprague-Dawley (SD) rats. Gastric water loading was induced either by oral gavage or an externalized indwelling stomach tube (20 mL x kg(-1) distilled water at body temperature). Repeated measurements after oral gavage were obtained with and without water loading and with and without ANG II receptor block (saralasin, 1.3 microg x kg(-1) x min(-1) iv). At 15 min after water loading by oral gavage, ventilation (V, 1.14+/-0.08 L x kg(-1) x min(-1)) and tidal volume (10.7+/-0.6 mL x kg(-1)) were transiently higher (P < 0.05), at a time when plasma osmolality was decreased (-8+/-1 mOsm), compared with gavage tube alone (0.95+/-0.08 L x kg(-1) min(-1) and 9.1+/-0.7 mL x kg(-1), respectively). However, water loading via stomach tube did not stimulate V; only during the 60-s period of water infusion did V increase briefly, but this was due to increased respiratory frequency. Dye indicators demonstrated that oral gavage exposes upper airway and esophageal afferents to water, presumably accounting for respiratory stimulation. Lesions of the SFO did not affect respiration or metabolism. A decrease in osmolality, associated with both water loading techniques, caused a sustained increase in oxygen consumption (Vo2 ) and a decrease in the V/Vo2 ratio. ANG II receptor block reduced the Vo2 response and prevented the decrease in V/Vo2 following water loading by oral gavage, but did not affect the transient stimulation of V. Unlike larger mammals, decreased osmolality does not stimulate respiration in the SD rat.