Effects of distention of the small intestine on the movements of the gallbladder and the sphincter of Oddi

1. Dogs anesthetized with pentobarbital sodium were mainly used and effects of the distention of the small intestine on the movements of the gall bladder and the sphincter of Oddi were investigated. 2. The distention of the small intestine (jejunum or ileum) inhibited the rhythmic contraction of the gall bladder and duodenal movements, and relaxed the tone of the sphincter of Oddi, resulting in an increase of the outflow of fluid through the orifice of the common bile duct. 3. After cutting the bilateral thoracic splanchnic nerves together with extirpation of the bilateral upper lumbar sympathetic trunks, the inhibitory response on the movements of the gall bladder and the tone of the sphincter of Oddi was completely abolished. The vagus nerve did not take part in the reflex response described above. The transection of the spinal cord at the level between Thl and Th2 produced no change in the reflex responses. 4. Fwm the results described above it may be supposed that effects of the distention of the small intestine on the movements of the gall bladder and the sphincter of Oddi are produced via the thoracic and lumbar splanchnic nerves through the reflex center which is located in the spinal cord.</p

Conduction of activity between muscles in the terminal region of the common bile duct and in the neighboring duodenum

The relationship between muscle activity at the terminal region of the common bile duct and the duodenal muscle was examined in rabbits. The rhythmic muscle activity in the terminal region was synchronous with duodenal muscle activity. The activity of the latter muscle preceded the former. The activity at the terminal region synchronous with the rhythmic activity of the duodenal muscle sometimes disappeared spontaneously. The muscle activity of the ampulla and the spincter at the terminal region was sometimes independently lost. The conduction of excitation from the duodenal muscle to the terminal region appeared to be performed at several sites. The existence of a &#34;conduction-shunt path&#34; between the terminal region and the duodenum, as well as between the ampulla and the sphincter appeared probably. Some quantitative differences were found between the spincter, ampulla and duodenum in inhibitory effects to stimulation of splanchnic nerves and reflex effects and to excitatory effects of cholecystokinin-pancreoxymin and caerulein. These results seem to indicate that the sympathetic nerves and the intramural cholinergic neurones controlling these region carry out activities quantitatively different from each other.</p

Effects of caerulein on the gastric motility of rats.

The effects of caerulein on gastric motility in urethane-anesthetized rats were studied. Caerulein administered into the lateral cerebral ventricle (i.c.v.) and jugular vein (i.v.) caused predominantly an inhibitory effect on gastric motility but sometimes an excitatory or a biphasic effect. The inhibitory response was reduced after vagotomy and/or splanchnicotomy, or after guanethidine. The remaining inhibitory response was abolished by tetrodotoxin, but was resistant to atropine and guanethidine. The excitatory response was abolished by atropine. Discharges of the gastric branch of the vagus nerve were decreased by i.v. injection of caerulein but increased by i.c.v. injection, whereas those of the splanchnic nerve were increased by both i.v. and i.c.v. injection. These results suggest that caerulein causes an inhibition of gastric motility by centrally stimulating vagal non-adrenergic inhibitory nerves and splanchnic adrenergic nerves and inhibiting vagal cholinergic nerves, and by peripherally stimulating non-adrenergic inhibitory neurons of the myenteric plexus. This peptide causes an excitation by stimulating cholinergic neurons of the myenteric plexus.</p

Participation of the parasympathetic and sympathetic nerves in regulation of gallbladder motility in the dog.

The participation of the parasympathetic and sympathetic nerves in the canine gallbladder motility was examined. Efferent stimulation of the parasympathetic (vagus) and sympathetic (celiac) nerves caused contraction or inhibition of the neck, body and fundus of the gallbladder. The contractile response induced by vagus nerve stimulation was reduced by subthreshold efferent stimulation of the celiac nerve, while the inhibitory response was neither reduced nor enhanced by subthreshold efferent stimulation of the celiac nerve. The contractile and inhibitory response induced by celiac nerve stimulation was not reduced in the neck, body and fundus by subthreshold efferent stimulation of the vagus nerve. The contractile response to vagus nerve stimulation was reversed to a relaxant response by atropine administration, which was reduced or abolished by hexamethonium. It is suggested that the vagus nerve-induced contractile response in the canine gallbladder is modulated by sympathetic nerves presynaptically at the vagus nerve endings in the enteric ganglion, but the vagus nerve-induced relaxant response, which probably was induced by non-adrenergic non-cholinergic inhibitory neurons, is not modulated by the sympathetic nerves.</p

Interaction of myenteric neurons and extrinsic nerves in the intestinal inhibitory response induced by mesenteric nerve stimulation.

Effects of the mesenteric nerve stimulation (MNS) on the twitch contraction induced by field stimulation were investigated regarding the relationship between myenteric neurons and extrinsic cholinergic nerves in the guinea-pig mesenteric nerve-ileal preparation. The twitch contraction was inhibited after MNS. The inhibition of the twitch contraction after MNS was induced twice, just after MNS (1st inhibition) and 2-3 min later (2nd inhibition) (type I), or once, just after MNS (1st inhibition) (type II), in recovery course of twitch contraction for 6-8 min. The 1st inhibition was slightly decreased by guanethidine and hexamethonium. The inhibitory response (1st inhibition) in both types I and II was recovered to the control level by pretreatment with naloxone (recovered twitch contraction), but the late inhibitory response (2nd inhibition) was markedly observed after 2-3 min in types I and II. Either the 1st or the 2nd inhibition was not altered by capsaicin, desensitization to calcitonin gene-related polypeptide (CGRP), vasoactive intestinal polypeptide (VIP), somatostatin, or galanin. The recovered twitch contraction in types I and II was decreased by CGRP-desensitization, or capsaicin. These results suggest that the first inhibitory response was induced by enteric opioid neurons connected with extrinsic cholinergic nerves, but the 2nd inhibition was induced by unknown substances other than CGRP, VIP, somatostatin, and galanin. The twitch contraction may partly be induced by endogenous neurokinin-like substances. And, some CGRP containing neurons, which connect with extrinsic cholinergic nerves, probably activate the intrinsic excitatory neurons.</p

On the gastrocecal inhibitory reflex in the rat.

In rats anesthetized with urethane, the effects of distention of the stomach upon cecal motility and neural mechanisms which generate this effect were studied. Cecal motility was inhibited which generate this effect were studied. Cecal motility was inhibited when the pars glandularis of the stomach was distended by pressure ranging from 25 to 30 cm H2O. This inhibitory reflex was not affected by bilateral cervical vagotomy, but completely abolished following bilateral severance of the greater splanchnic nerves or after intravenous administration of guanethidine. After transection of the spinal cord at the level of the 5th thoracic segment the inhibitory reflex remained intact, but was abolished following pithing of the 6th thoracic segment and below. It may be concluded that the afferent and efferent path of the gastrocecal inhibitory reflex mainly pass through the greater splanchnic nerves and the reflex center is located in thoracic segments caudal to the 6th thoracic segment.</p

On the intestinal extrinsic reflexes elicited from the small in­testine

Effects of stimulation of the small intestine upon the gastric, small intestinal and colonic motility have been studied in dogs. The results are summarized as follows. 1. The movements of the stomach, small intestine, and proximal colon are always inhibited by the distension or the contracture of the muscular coats of the small intestine but no responses are produced by a mechanical or chemical stimulation of the mucosa; and those of the distal colon are in most cases also inhibited, whereas in rare instances are they augmented. 2. The afferent impulses are transmitted through the great and small splanchnic nerves and the lumbar sympathetic nerves to the inhibitory as well as the excitatory (pelvic nuclei) centers of the intestinal movements located within the spinal cord, whereas the vagal nuclei remain unaffected. The efferent impulses are transmitted through the thoraco-lumbar sympathetic nerves as well as through the pelvic nerves. The latter are involved in the augmentative effect produced in the distal colon. 3. The threshold producing the extrinsic muscular reflex is higher than that eliciting the intrinsic muscular reflex.</p

Electrical behavior of myenteric neurons induced by mesenteric nerve stimulation in the guinea pig ileum.

Effects of mesenteric nerve (MN) stimulation on the electrophysiological behavior of myenteric neurons in the guinea pig ileum were investigated with intracellular recording techniques in the myenteric flaps innervated with mesenteric nerves. MN stimulation at 0.11-6 Hz evoked fast excitatory postsynaptic potentials (EPSPs) in 6 myenteric neurons (2 Type 2/AH, 3 NS and 1 Type 1/S cells) and rarely evoked antidromic soma spike potentials in 3 myenteric neurons. Fast EPSPs were abolished by hexamethonium. Slow EPSPs evoked by MN stimulation (Takaki and Nakayama (1988) Brain Res., 442, 351-353) were also obtained in 5 Type 2/AH neurons and were irreversibly abolished by superfusion with capsaicin 10 microM. It is, therefore, likely that fast EPSPs mediated by nicotinic cholinergic receptors are due to stimulation of the vagus nerve and slow EPSPs are mediated by a release of substance P at axosomatic synapses due to antidromic activation of the capsaicin-sensitive sensory nerves.</p

Effect of motilin on the sphincter of Oddi in the dog.

To investigate the action of motilin on the sphincter of Oddi, the flow rate of the perfusate (FRP) discharged into the duodenal lumen through the orifice of the common bile duct was measured by means of an electric drop counter in decerebrated dogs. Motilin in doses above 0.5 micrograms/kg i.v. reduced or stopped the FRP. The fifty percent recovery time of FRP was 20 min and full recovery time was 30 min. The reduction of FRP induced by motilin was unaffected by denervation and atropinization. These results suggest that motilin caused an increase in tone of the sphincter of Oddi by acting on the sphincter muscle.</p

Atropine-sensitive, tetrodotoxin-resistant contraction induced by noradrenaline in isolated cat rectum.

Effects of noradrenaline (NA) on the isolated rectal circular muscle of the cats were studied in comparison with the effects on the internal anal sphincter (IAS). NA (10(-8)-10(-7) g/ml) caused tonic contraction in four of 15 strips of the rectum taken from 15 animals, and in all 15 strips of the IAS. Phenylephrine also induced rectal and IAS contraction. Rectal contraction induced by NA was resistant to phentolamine, yohimbine, propranolol, hexamethonium and tetrodotoxin, but blocked by atropine. IAS contraction induced by NA was resistant to propranolol, atropine, hexamethonium and tetrodotoxin, but blocked by phentolamine and yohimbine. It is suggested that an atropine-sensitive excitatory adrenergic mechanism other than the excitatory alpha-adrenergic mechanism exists in the rectal circular muscle.</p