GABAA- and GABAB-receptor-mediated modification of intestinal motility

The actions of γ-aminobutyric acid (GABA) and its analogues, 3-amino-1-propanesulphonic acid (3APS) and baclofen, have been investigated using isolated segments of the guinea-pig ileum and distal colon. GABA and 3APS, but not baclofen, induced GABA_A-receptor mediated effects; prompt, dose-dependent contractions of the ileum which were antagonised by bicuculline, picrotoxinin, piretanide, tetramethylenedisulphotetramine, atropine and tetrodotoxin. Baclofen and GABA, but not 3APS, induced a dose-dependent GABA_B-receptor mediated depression of electrically elicited twitch contractions of the ileum, unaffected by the GABA_A-receptor antagonists or by antagonism of adenosine, adrenergic, opiate or nicotinic receptors. In the distal colon, baclofen and GABA caused a bicuculline- and picrotoxinin-intensitive depression of spontaneous cholinergic contractions. Desensitization to GABA and baclofen, and cross-desensitization to both agonists was observed. Combined antagonism of GABA_A-receptors and desensitization to baclofen slowed pellet expulsion to the same extent as GABA desensitization alone, indicating that both GABA_A- and GABA_B-receptor sites are involved in this modification of peristalsis by GABA.     

Studies on the mechanism of the action of morphine on the peristalsis of guinea pig ileum in situ

Summary The influence of some drugs on the effect of morphine on the threshold pressure required to elicit peristalsis in the guinea pig ileum in situ was studied, in order to test the hypothesis that this effect of morphine is mediated by catecholamine release.Tachyphylaxis to this effect of morphine was confirmed. Pretreatment with two 8 mg/kg doses of reserpine, 24 and 48 hrs before the experiment, significantly reduced the effect of morphine on the pressure threshold. The i.v. administration of 10 mg/kg dl-Dopa re-established the effect of morphine in reserpinized animals to the level of the untreated controls. Pretreatment with guanethidine (15 mg/kg) decreased and even prevented this effect of morphine. Phentolamine pretreatment (10 mg/kg) also significantly inhibited the effect of morphine. Neither DCI nor propranolol influenced this morphine effect. Pretreatment with reserpine, guanethidine or phentolamine reduced the basic pressure threshold needed to elicit peristalsis.The possibility that the decrease of local circulation induced by hypotension would reduce the local concentration of morphine was rejected because the same doses of guanethidine or phentolamine did not modify the effect of hexamethonium given i.v. in this preparation.All these results support the idea that the effect of morphine on intestinal peristalsis is mediated by a catecholamine acting on -receptors, e. g. norepinephrine.     

异丙酚对小白鼠胃肠道蠕动功能的影响

】     

Interstitial cells of Cajal, the Maestro in health and disease

Interstitial cells of Cajal (ICC) are important players in the symphony of gut motility. They have a very signif icant physiological role orchestrating the normal peristaltic activity of the digestive system. They are the pacemaker cells in gastrointestinal (GI) muscles. Absence, reduction in number or altered integrity of the ICC network may have a dramatic effect on GI system motility. More understanding of ICC physiology will foster advances in physiology of gut motility which will help in a future break...     

Neuronal analysis of pharyngeal peristalsis in the gastropod Navanax in terms of identified motoneurons innervating identified muscle bands. II. Radial and circumferential motor fields

The neuronal basis of pharyngeal ingestion and peristalsis was studied in the gastropod Navanax inermis. Radially and circumferentially oriented muscles produced expansion and constriction of the pharynx. Motor fields of 11 identified radial motoneurons and 13 identified circumferential motoneurons were determined with respect to circumferential and longitudinal muscle band coordinates by muscle movements, electromyography, antidromic stimulation and axonal anatomy. Activation of these identified motoneurons can account for all the elemental pharyngeal movements observed during feeding. Four motoneurons, each innervating most of radial muscle, can mediate ingestion. Three radial motoneurons with anterior motor fields can mediate anterior expansion during sealing of the pharyngeal lips around prey and during regurgitation. Ten circumferential motoneurons have small arciform motor fields, the distributions of which correspond to the regional specializations in circumferential band organization. Arciform constriction can center eccentric ingested prey within the pharyngeal lumen during peristalsis. Arciform constrictions could combine to form an annular constriction in peristalsis. Small, non-overlapping, circumferential motor fields maximize the number of independent annular units available to produce a fine peristaltic wave. Sphincters have more circumferential motoneurons with smaller motor fields; this innervation permits finer motor control. Radial motoneurons with posterior motor fields can produce expansion caudal to a circumferential constriction during peristalsis. Motor fields of regional radial motoneurons show greater interanimal variability than circumferential motor fields, which is correlated with a less essential role of radial motoneurons in peristalsis. Two circumferential motoneurons with giant posterior pharyngeal motor fields can mediate pharyngeal emptying either in swallowing or in regurgitation.     

Differential effects of SKF 10,047 (N-allyl-normetazocine) on peristalsis and longitudinal muscle contractions of the isolated guinea-pig ileum

Summary The purpose of this study was to investigate the differential involvement of distinct types of opioid receptors in the modulation of intestinal peristalsis compared to electrically induced longitudinal muscle contractions.Like naloxone, the proposed -agonist and -antagonist SKF 10,047 (N-allyl-normetazocine) dose-dependently enhanced peristaltic circular muscle contractions in the isolated guinea-pig ileum. Pre-application of SKF 10,047 at a concentration which itself enhanced peristalsis by 20% on average strongly attenuated the inhibition of peristalsis produced by opioids previously proposed to act via -opioid-receptors in the guinea-pig ileum, i.e. normorphine, -endorphin, d-Ala²-d-Leu⁵-enkephalin and d-Ser²-l-Leu⁵-enkephalyl-Thr, but less strongly attenuated the inhibition produced by compounds suggested to act via -opioid-receptors in this tissue, i.e. ethylketazocine and dynorphin (1–13). In contrast to its effect on peristalsis, SKF 10,047 inhibited the electrically induced contractions of the myenteric plexus-longitudinal muscle preparation in a naloxonereversible fashion.It may be concluded that - and -opioid receptors are of a greater functional significance than -receptors in the control of peristalsis. -Receptors might participate predominantly in modulating the release of acetylcholine which underlies the electrically induced longitudinal muscle contraction.     

Normal Functional Luminal Imaging Probe Panometry Findings Associate With Lack of Major Esophageal Motility Disorder on High-Resolution Manometry

1. Download : Download high-res image (374KB)
2. Download : Download full-size image