Home  About us  Contact
 

Mechanical Activity (mechanical + activity)

Distribution by Scientific Domains
Medical Sciences100%

Selected Abstracts

Circadian patterns of gastric electrical and mechanical activity in dogs

NEUROGASTROENTEROLOGY & MOTILITY, Issue 1 2008
R. Aviv
Abstract, Gastric motor function assessment, in humans and animals, is typically performed for short recording periods. The aim of this article was to monitor gastric electrical and motor activity in the antrum and fundus simultaneously, for long periods, using a new implantable system. Ten dogs were implanted with fundic and antral electrodes for assessment of impedance and electrical activity. Dogs were studied while in cages, for periods of 22,26 h. From late evening and until feeding on the next day, slow wave (SW) rhythm demonstrated a distinct pattern of intermittent pauses (mean duration = 22.8 ±4.1 s) that delineated groups of SW's. Phasic increases in fundic tone were seen mostly in association with SW pauses, and were highly correlated with antral contractions, R2 = 0.652, P < 0.05. The SW rate (events per minute) in the postprandial period, fasting and night time was 4.2 ± 0.2, 5 ± 0.2 and 4.7 ± 0.3, respectively, P < 0.05 postprandial vs other periods. Antral and fundic mechanical activities were highly correlated during fasting, particularly at night. This novel method of prolonged gastric recording provides valuable data on the mechanical and electrical activity of the stomach, not feasible by current methods of recording. During fasting, fundic and antral motor activities are highly correlated and are associated with periodic pauses in electrical activity. [source]

Effects of extrinsic denervation on innervation with VIP and substance P in circular muscle of rat jejunum,

NEUROGASTROENTEROLOGY & MOTILITY, Issue 7 2008
M. S. Kasparek
Abstract, Extrinsic denervation contributes to enteric motor dysfunction after small bowel transplantation (SBT). Our aim was to determine changes in nonadrenergic, noncholinergic innervation with vasoactive intestinal polypeptide (VIP) and substance P (Sub P) in rat jejunal circular muscle after SBT. Muscle strips were studied in tissue chambers from six groups of rats (n , 6 per group): naïve controls (NC), animals 1 week after anaesthesia/sham celiotomy (SC-1), and 1 and 8 weeks after jejunal and ileal transection/reanastomosis (TA-1, TA-8) and after syngeneic, orthotopic SBT (SBT-1, SBT-8). Response to exogenous VIP and Sub P and their endogenous release during electrical field stimulation (EFS) were studied. Exogenous VIP and Sub P caused a dose-dependent inhibition and stimulation of mechanical activity in all groups respectively (P < 0.05). The responses to VIP and Sub P were decreased (compared to NC) in all groups at 1 and 8 weeks postoperatively. The VIP antagonist ([d - p -Cl-Phe6,Leu17]-VIP) did not prevent the inhibition by exogenous VIP in any group, while the Sub P antagonist ([d -Pro2,d -Trp7,9]-Sub P) prevented the effect of exogenous Sub P in NC, TA-8 and SBT-8 (P < 0.05). Responses to exogenous VIP were unaffected by the nitric oxide synthase inhibitor l - NG -nitro arginine and precontraction of muscle strips with Sub P. Endogenous release of VIP and Sub P during EFS was preserved after SBT. In circular muscle of rat jejunum, changes in neuromuscular transmission with VIP and Sub P during the first 8 weeks after SBT are not mediated by extrinsic denervation. [source]

Circadian patterns of gastric electrical and mechanical activity in dogs

NEUROGASTROENTEROLOGY & MOTILITY, Issue 1 2008
R. Aviv
Abstract, Gastric motor function assessment, in humans and animals, is typically performed for short recording periods. The aim of this article was to monitor gastric electrical and motor activity in the antrum and fundus simultaneously, for long periods, using a new implantable system. Ten dogs were implanted with fundic and antral electrodes for assessment of impedance and electrical activity. Dogs were studied while in cages, for periods of 22,26 h. From late evening and until feeding on the next day, slow wave (SW) rhythm demonstrated a distinct pattern of intermittent pauses (mean duration = 22.8 ±4.1 s) that delineated groups of SW's. Phasic increases in fundic tone were seen mostly in association with SW pauses, and were highly correlated with antral contractions, R2 = 0.652, P < 0.05. The SW rate (events per minute) in the postprandial period, fasting and night time was 4.2 ± 0.2, 5 ± 0.2 and 4.7 ± 0.3, respectively, P < 0.05 postprandial vs other periods. Antral and fundic mechanical activities were highly correlated during fasting, particularly at night. This novel method of prolonged gastric recording provides valuable data on the mechanical and electrical activity of the stomach, not feasible by current methods of recording. During fasting, fundic and antral motor activities are highly correlated and are associated with periodic pauses in electrical activity. [source]

Control of non-adrenergic non-cholinergic reflex motor responses in circular muscle of guinea-pig small intestine by Met-enkephalin

AUTONOMIC & AUTACOID PHARMACOLOGY, Issue 4 2002
Chr. Ivancheva
Summary 1 A triple organ bath method allowing the synchronous recording of the motor activity of the circular muscle layer belonging to the oral and anal segments of guinea-pig small intestine adjacent to an electrically stimulated middle segment was developed to study the ascending and descending reflex motor responses. 2 Electrical field stimulation (0.8 ms, 40 V, 5 Hz, 10 s) applied to the middle part of the segments elicited tetrodotoxin (1 ,m)-sensitive ascending and descending contractile responses of the nonstimulated parts, oral and anal, respectively. The ascending contraction was more pronounced as compared with the descending contraction. 3 In the presence of phentolamine (5 ,m), propranolol (5 ,m) and atropine (3 ,m) a significant decrease in the amplitude of the ascending contraction was seen and a descending relaxation, instead of a contraction was observed. 4 Met-enkephalin applied at a single concentration (0.1 ,m) or cumulatively (0.001,1 ,m) inhibited both non-adrenergic non-cholinergic (NANC) descending relaxation and ascending contraction with similar efficacy but different potency, IC50 being 5.9 ± 0.3 and 39.0 ± 4 nm, respectively. Naloxone (0.5 ,m) prevented the effects of Met-enkephalin. 5 L-NNA (0.5 mm), an inhibitor of nitric oxide synthesis, increased the ascending contraction and strongly reduced but not abolished the descending relaxation. l -Arginine (0.5 mm) restored the motor responses to the initial level in l -NNA-pretreated preparations, d -Arginine (0.5 nm) had no effects. 6 Met-enkephalin (0.1 ,m) depressed the l -NNA-dependent increase of the ascending contraction and failed to change the l -NNA-resistant part of the descending relaxation. 7 Met-enkephalin did not alter spontaneous NANC mechanical activity. SNP (1 or 10 ,m), an exogenous donor of nitric oxide, caused a concentration-dependent relaxation. The effects of SNP persisted in Met-enkephalin (0.1 ,m)-pretreated preparations. 8 NANC reflex ascending contraction and descending relaxation were synchronously induced by a local nerve stimulation indicating a functional coactivation of NANC orally projected excitatory and anally directed inhibitory pathways. Acting prejunctionally, Met-enkephalin provided a negative controlling mechanism inhibiting both ascending and descending, mainly nitric oxide mediated, reflex responses. A higher sensitivity of the descending relaxation to Met-enkephalin was observed suggesting an essential role of opioid(s) in reducing the efficacy of descending motor activity. [source]

Role of NK1 and NK2 receptors in mouse gastric mechanical activity

BRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2006
Flavia Mulè
The aim of the present study was to examine the role of NK1 and NK2 receptors in the control of mechanical activity of mouse stomach. In this view, the motor effects induced by NK1 and NK2 receptor agonists and antagonists were analyzed, measuring motility as intraluminal pressure changes in mouse-isolated stomach preparations. In parallel, immunohistochemical studies were performed to identify the location of NK1 and NK2 receptors on myenteric neurons and smooth muscle cells. Substance P (SP) induced biphasic effects: a contraction followed by relaxation; neurokinin A (NKA) and [, -Ala8]-NKA(4,10), selective agonist of NK2 receptors, evoked concentration-dependent contractions, whereas [Sar9, Met(O2)11]-SP, selective agonist of NK1 receptors, induced concentration-dependent relaxation. SR48968, NK2 receptor antagonist, did not modify the spontaneous activity and reduced the contractile effects induced by tachykinins without affecting the relaxation. SR140333, NK1 receptor antagonist, did not modify the spontaneous activity and antagonized the relaxant response to tachykinins, failing to affect the contractile effects. The relaxation to SP or to [Sar9, Met(O2)11]-SP was abolished by tetrodotoxin (TTX) and significantly reduced by N -nitro- L -arginine methyl ester (L -NAME). NK2 -immunoreactivity (NK2 -IR) was seen at the level of the smooth muscle cells of both circular and longitudinal muscle layers. NK1 -immunoreactive (NK1 -IR) neurons were seen in the myenteric ganglia and NK1/nNOS double labeling revealed that some neurons were both NK1 -IR and nNOS-IR. These results suggest that, in mouse stomach, NK1 receptors, causing relaxant responses, are present on nitrergic inhibitory myenteric neurons, whereas NK2 receptors, mediating contractile responses, are present at muscular level. British Journal of Pharmacology (2006) 147, 430,436. doi:10.1038/sj.bjp.0706645 [source]