Downregulation of neutral endopeptidase (EC 3.4.24.11) in the inflamed rat intestine

1993 ◽  
Vol 264 (4) ◽  
pp. G735-G743 ◽  
Author(s):  
L. Hwang ◽  
R. Leichter ◽  
A. Okamoto ◽  
D. Payan ◽  
S. M. Collins ◽  
...  
Keyword(s):  
Substance P ◽  
Myenteric Plexus ◽  
Longitudinal Muscle ◽  
Intestinal Inflammation ◽  
Specific Activity ◽  
Trichinella Spiralis ◽  
Extracellular Fluid ◽  
Circular Muscle ◽  
Neutral Endopeptidase ◽  
Jejunal Mucosa

Intestinal inflammation induced by the nematode Trichinella spiralis is accompanied by increased intestinal concentrations of substance P, a mediator of inflammation and a stimulant of smooth muscle contraction, and by intestinal hypermotility. The expression of neutral endopeptidase (NEP), a cell surface enzyme that degrades substance P in the extracellular fluid, was examined in the inflamed intestine. NEP enzymatic activity, measured by a fluorometric assay, was reduced by 84-fold in jejunal mucosa-circular muscle and by 12-fold in jejunal longitudinal muscle-myenteric plexus within 6 days after infection with T. spiralis. The downregulation was unaffected by treatment with betamethasone and was still observed in athymic animals. NEP protein levels, examined by Western blotting, confirmed the loss of NEP from inflamed tissue. The specific activity for degradation of substance P was reduced by sixfold in jejunal mucosa-circular muscle and by twofold in jejunal longitudinal muscle-myenteric plexus of rats infected with T. spiralis compared with uninfected controls. Thus the downregulation of NEP resulted in reduced substance P degradation, which may contribute to functional abnormalities of the inflamed intestine.

Altered expression of sodium pump isoforms in the inflamed intestine of Trichinella spiralis-infected rats

1993 ◽  
Vol 264 (6) ◽  
pp. G1160-G1168 ◽  
Author(s):  
I. Khan ◽  
S. M. Collins
Keyword(s):  
Sodium Pump ◽  
Longitudinal Muscle ◽  
Trichinella Spiralis ◽  
Internal Standard ◽  
Circular Muscle ◽  
Northern Analysis ◽  
Jejunal Mucosa ◽  
Altered Expression ◽  
Altered Regulation ◽  
Polymerase Chain

We used polymerase chain reaction (PCR) and Northern analysis to examine the effect of Trichinella spiralis infection on mRNA expression of sodium pump isoforms in rat intestine. 28S RNA was coamplified as an internal standard, and the abundance of the isoformic mRNA was expressed relative to 28S RNA. As assessed by PCR and Northern analysis, the alpha 1- and beta 1-subunits were expressed in the jejunum and ileum of noninfected control rats. However, in the jejunum the levels were suppressed after 24 h of infection. The suppression became maximal by day 6 and was reversed to normal by day 23 postinfection (PI). In contrast, no suppression was observed in the noninflamed ileum of infected rats. Further analysis revealed that alpha 1-mRNA was suppressed in jejunal mucosa by 89% and in longitudinal muscle-myenteric plexus by 62% but was not suppressed in circular muscle. Western blot analysis revealed a 61% decrease in the alpha 1-subunit protein in the mucosa and a 62% decrease in longitudinal muscle, whereas there was no change in the alpha 1-protein in circular muscle on day 6 PI. In contrast, marked (89%) suppression of beta 1-mRNA was observed only in the mucosa; there was no change in either circular or longitudinal muscle on day 6 PI. These results indicate that T. spiralis infection in the rat is accompanied by a significant decrease in the alpha 1-subunit of the sodium pump in longitudinal muscle. This reduction could result from altered regulation involving pretranslational changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Somatostatin modulation of peptide-induced acetylcholine release in guinea pig ileum

1984 ◽  
Vol 246 (5) ◽  
pp. G509-G514 ◽  
Author(s):  
D. H. Teitelbaum ◽  
T. M. O'Dorisio ◽  
W. E. Perkins ◽  
T. S. Gaginella
Keyword(s):  
Substance P ◽  
Guinea Pig ◽  
Myenteric Plexus ◽  
Acetylcholine Release ◽  
Longitudinal Muscle ◽  
Guinea Pig Ileum ◽  
Gut Motility ◽  
Release Of Acetylcholine

The peptides caerulein, neurotensin, somatostatin, and substance P modulate the activity of intestinal neurons and alter gut motility. We examined the effects of these peptides on acetylcholine release from the myenteric plexus and intestinal contractility in vitro. Caerulein (1 X 10(-9) M), neurotensin (1.5 X 10(-6) M), and substance P (1 X 10(-7) M) significantly enhanced the release of [3H]acetylcholine from the myenteric plexus of the guinea pig ileum. This effect was inhibited by tetrodotoxin (1.6 X 10(-6) M). Somatostatin (10(-6) M) inhibited caerulein- and neurotensin-evoked release of acetylcholine but did not inhibit release induced by substance P. Caerulein, neurotensin, and substance P caused contraction of the guinea pig ileal longitudinal muscle. Somatostatin inhibited the contractions induced by caerulein and neurotensin. In contrast, substance P-induced contraction was not inhibited significantly by somatostatin. Thus, in the guinea pig ileum, caerulein-, neurotensin-, and substance P-induced contractility is due, at least in part, to acetylcholine release from the myenteric plexus. The ability of somatostatin to inhibit peptide-induced contractility is selective, and its mechanism may be attributed to inhibition of acetylcholine release.

Characterization of the effects of neurokinins on canine antral muscle

1988 ◽  
Vol 255 (6) ◽  
pp. G779-G786
Author(s):  
C. B. Koelbel ◽  
E. A. Mayer ◽  
G. van Deventer ◽  
W. J. Snape ◽  
A. Patel
Keyword(s):  
Substance P ◽  
Mechanical Response ◽  
Longitudinal Muscle ◽  
Rank Order ◽  
Circular Muscle ◽  
Neurokinin A ◽  
Inotropic Response ◽  
Chronotropic Response ◽  
Natural Ligand ◽  
Dose Dependent

The excitation of longitudinal antral muscle by substance P (SP) involves both a myogenic and a cholinergic effect. To examine if these responses are mediated by different neurokinin receptors, we studied the mechanical response and the release of [3H]acetylcholine from antral muscle strips in response to SP, substance P methylester (SPME), neurokinin A (NKA), neurokinin B (NKB), and several non-mammalian tachykinins. All peptides studied showed a dose-dependent inotropic and chronotropic effect on spontaneous phasic contractions. This ionotropic effect in longitudinal muscle was partially atropine sensitive for SPME, SP, and NKB but not for NKA, whereas neither atropine nor tetrodotoxin had an effect in circular muscle. In longitudinal muscle, all three neurokinins were equipotent. In longitudinal muscle treated with atropine and in circular muscle, the rank order of potency for the inotropic response was NKA greater than NKB greater than SP greater than SPME. For the chronotropic response the rank order was SPME, SP greater than NKA greater than NKB. NKA, NKB, and SP caused a dose-dependent, tetrodotoxin-sensitive increase in [3H]acetylcholine release from strips preincubated with [3H]choline. NKA was significantly more potent to release [3H]acetylcholine than either NKB or SP. The stimulated release was inhibited by [D-Ala2,D-Met5]methionine enkephalinamide and the SP antagonist, spantide. These results are consistent with the hypothesis that NKA is the natural ligand mediating the myogenic inotropic response in both muscle layers and the cholinergic response in longitudinal muscle.

Substance P and CGRP mediate motor response of rabbit colon to capsaicin

1990 ◽  
Vol 259 (5) ◽  
pp. G889-G897 ◽  
Author(s):  
E. A. Mayer ◽  
C. B. Koelbel ◽  
W. J. Snape ◽  
V. Eysselein ◽  
H. Ennes ◽  
...  
Keyword(s):  
Substance P ◽  
Longitudinal Muscle ◽  
Contractile Activity ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Inhibitory Effect ◽  
Nerve Fibers ◽  
Repeated Exposure ◽  
Nerve Terminals ◽  
Rabbit Colon

Primary afferent nerve terminals located in the mammalian gut wall may play a role in region-specific modulation of gastrointestinal motility. In the present study, we sought to characterize the effect of neuropeptides released from these afferents by capsaicin (CAP) on contractile activity of smooth muscle from the distal rabbit colon. CAP caused a release of acetylcholine and immunoreactivity for substance P (SP) and calcitonin gene-related peptide (CGRP) from the muscle coat. CAP caused a dose-dependent transient stimulation of longitudinal muscle contractions, followed by prolonged inhibition of spontaneous but not stimulated contractile activity. The initial stimulation was abolished by the SP antagonist spantide and by atropine. The inhibitory effect was reduced by repeated exposure of muscle to CGRP. The effect of CGRP on spontaneous contractions differed between longitudinal and circular muscle. In longitudinal muscle, a stimulation was preceded by a transient inhibition, whereas in circular muscle, only inhibition was seen. Both effects were resistant to tetrodotoxin. Repeated exposure of circular but not longitudinal muscle to CGRP resulted in a disappearance of the peptide's inhibitory effect. Exogenously applied CGRP was only a weak antagonist of contractions stimulated by SP and bethanechol. These findings suggest that in the rabbit colon at least the following two neuropeptides are released from CAP-sensitive nerve fibers: a neurokinin peptide from nerve terminals located within the myenteric plexus and CGRP from terminals probably located within the circular muscle layer.

Regional cholinergic differences between distal and proximal colonic myenteric plexus

1990 ◽  
Vol 258 (3) ◽  
pp. G404-G410 ◽  
Author(s):  
W. L. Hasler ◽  
S. Kurosawa ◽  
O. Y. Chung
Keyword(s):  
Myenteric Plexus ◽  
Regional Differences ◽  
Acetylcholine Release ◽  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Distal Colon ◽  
Proximal Colon ◽  
Maximal Response ◽  
Total Tissue ◽  
Cholinergic Response

We investigated differences in myogenic and neural response of proximal vs. distal guinea pig colon in longitudinal and circular muscle. Spontaneous phasic contractions were more intense in distal colon in both layers. Phasic contractile frequency was also greater in distal colon in both layers. In both longitudinal and circular muscle, acetylcholine induced greater contractions in distal than in proximal colon (maximal response: longitudinal, 7.00 +/- 1.04 X 10(4) vs. 3.50 +/- 0.49 X 10(4) N/m2; circular, 3.29 +/- 0.82 X 10(4) vs. 8.92 +/- 1.30 X 10(3) N/m2). Compared with proximal colon, electric field stimulation induced greater atropine-sensitive contractions in distal colon in both muscle layers (maximal response: longitudinal, 4.22 +/- 0.53 X 10(4) vs. 7.53 +/- 1.97 X 10(3) N/m2; circular, 2.14 +/- 0.79 X 10(3) vs. -5.28 +/- 2.04 X 10(2) N/m2). In contrast, there were no regional differences in atropine-insensitive relaxations. Veratridine (10(-5) M) stimulated greater [3H]acetylcholine release from distal longitudinal muscle-myenteric plexus than from proximal preparations (11.44 +/- 2.03 vs. 5.84 +/- 1.26% of total tissue radioactivity). These data suggest the greater contractile responses in the distal colon are because of enhanced cholinergic response to neural stimuli and increased muscle sensitivity to acetylcholine, whereas there are no differences in the inhibitory responses to neural stimuli.

Gap junctions in gastrointestinal muscle contain multiple connexins

2001 ◽  
Vol 281 (2) ◽  
pp. G533-G543 ◽  
Author(s):  
Y. F. Wang ◽  
E. E. Daniel
Keyword(s):  
Gastrointestinal Tract ◽  
Gap Junctions ◽  
Lower Esophageal Sphincter ◽  
Myenteric Plexus ◽  
Interstitial Cells Of Cajal ◽  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Esophageal Sphincter ◽  
Cells Of Cajal ◽  
Cx 43

In the canine gastrointestinal tract, the roles that gap junctions play in pacemaking and neurotransmission are unclear. Using antibodies to connexin (Cx)43, Cx45, and Cx40, we determined the distribution of these connexins. Cx43 was present in all locations where structural gap junctions occur. Cx40 was also widely distributed in the circular muscle of the lower esophageal sphincter (LES), stomach, and ileum. Cx45 was sparsely distributed in circular muscle of the LES. In the interstitial cells of Cajal (ICC) networks of myenteric plexus, in the deep muscular and submuscular plexuses, sparse Cx45 and Cx40 immunoreactivity was present. In colon, immunoreactivity was found only in the myenteric and submuscular plexus and nearby circular muscle cells. No immunoreactivity was found in sites lacking structural gap junctions (longitudinal muscle, inner circular muscle of the intestine, and most circular muscle of the colon). Studies of colocalization of connexins suggested that in the ICC networks, some colocalization of Cx43 with Cx40 and/or Cx45 occurred. Thus gap junctions in canine intestine may be heterotypic or heteromeric and have different conductance properties in different regions based on different connexin compositions.

Structural characterization of interstitial cells of Cajal in myenteric plexus and muscle layers of canine colon

1990 ◽  
Vol 68 (11) ◽  
pp. 1419-1431 ◽  
Author(s):  
I. Berezin ◽  
J. D. Huizinga ◽  
E. E. Daniel
Keyword(s):  
Myenteric Plexus ◽  
Interstitial Cells Of Cajal ◽  
Longitudinal Muscle ◽  
Structural Characteristics ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Interstitial Cells ◽  
The Other ◽  
Longitudinal Muscle Layer ◽  
Cells Of Cajal

We have carried out a detailed ultrastructural study of the interstitial cells near the myenteric plexus of the canine colon and defined the structural characteristics which distinguish them from other resident non-neural cells. We have also examined the interconnections of these interstitial cells with nerves, the longitudinal muscle, and the circular muscle. In addition, we sought connections between interstitial cells of the myenteric plexus and those described earlier at the inner border of the circular muscle in proximal and distal colon. The interstitial cells of the myenteric plexus were structurally distinctive, and made gap junctions with one another and occasionally with smooth muscle. There seemed to be two subsets of these interstitial cells, one associated with the longitudinal muscle and the other with the circular muscle. Cells of both subsets were often close (≤20 nm) to nerve profiles. The interstitial cells near the longitudinal muscle layer penetrated slightly into the muscle layer, but those near the circular muscle did not and neither set contacted the other. Moveover, interstitial cells of Cajal located near the myenteric plexus were never observed to contact those at the inner border of circular muscle. The interstitial cells of Cajal at the canine colon myenteric plexus are structurally organized to provide independent pacemaking activities for the longitudinal and adjacent circular muscle. Their dense innervation suggests that they mediate neural modulation of intestinal pacemaker activities. Moreover, they lack direct contacts with the interstitial cell network at the inner border of circular muscle, which is essential for the primary pacemaking activity of circular muscle. The structural organization of interstitial cells in canine colon is consistent with their proposed role in pacemaking activity of the two muscle layers.Key words: pacemakers, neuromodulation, interstitial cells of Cajal.

Regulation of excitatory neural input to longitudinal intestinal muscle by myenteric interneurons

1998 ◽  
Vol 275 (5) ◽  
pp. G973-G978 ◽  
Author(s):  
J. R. Grider
Keyword(s):  
Substance P ◽  
Myenteric Plexus ◽  
Neurotransmitter Release ◽  
Longitudinal Muscle ◽  
Distal Colon ◽  
Excitatory Input ◽  
Gaba Neurons ◽  
Inhibitory Pathways ◽  
Neural Input ◽  
Rat Distal Colon

The circuit of myenteric interneurons that regulate excitatory input to longitudinal colonic muscle was identified using dispersed ganglia and longitudinal muscle strips with adherent myenteric plexus from rat distal colon. The preparations enabled measurement of neurotransmitter release from interneurons and/or excitatory motoneurons innervating longitudinal muscle. 1,1-Dimethyl-4-phenylpiperizinium (DMPP) and somatostatin were used to activate myenteric neurons in dispersed ganglia and muscle strips, respectively. DMPP-stimulated vasoactive intestinal peptide (VIP) release in dispersed ganglia was inhibited by [Met]enkephalin and bicuculline and augmented by naloxone and GABA, implying that inhibitory opioid and stimulatory GABA neurons regulate the activity of VIP interneurons. In muscle strips, VIP stimulated basal and augmented somatostatin-induced substance P (SP) release; the somatostatin-induced increase in SP release was inhibited by VIP-(10—28) and N G-nitro-l-arginine, implying that excitatory VIP neurons regulate tachykinin motoneurons innervating longitudinal muscle. Somatostatin inhibited [Met]enkephalin and stimulated VIP release; basal and somatostatin-stimulated VIP release were inhibited by [Met]enkephalin and bicuculline and augmented by naloxone and GABA, implying that inhibitory pathways linking somatostatin, opioid, and GABA neurons regulate VIP interneurons, which in turn regulate tachykinin and probably cholinergic motoneurons.

Mechanics and neuropeptide responses of feline pylorus and gastric muscle in vitro

1989 ◽  
Vol 256 (5) ◽  
pp. G862-G867 ◽  
Author(s):  
A. Merlo ◽  
S. Cohen
Keyword(s):  
Substance P ◽  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Optimal Length ◽  
Pyloric Ring ◽  
Tension Properties ◽  
Gastric Muscle ◽  
Inferior Portion ◽  
Superior Portion

Mechanical properties and neuropeptide responses were compared for feline pyloric and gastric muscle under isometric conditions in vitro. Total tension in antral circular muscle (0.699 +/- 0.003 kg/cm2) was less than in corpus circular (1.597 +/- 0.007 kg/cm2) or longitudinal muscle from the lesser and greater curvatures (1.256 +/- 0.009 and 1.253 +/- 0.007 kg/cm2, n greater than or equal to 55, P less than 0.05). The components of tension at optimal length were similar for all gastric muscles (P greater than 0.1). The pylorus maintained less total tension (0.335 +/- 0.003 kg/cm2) and a greater component of resting tension (75.6%) than gastric muscle (P less than 0.01). Substance P, cholecystokinin-8 (CCK-8), and neurotensin varied in potency and efficacy in circular muscle of the antrum, corpus, and inferior portion of the pyloric ring. Longitudinal muscle and the superior portion of pylorus responded poorly if at all to neuropeptides. Substance P- but not CCK-8- or neurotensin-induced contractions of gastric muscle were reduced by tetrodotoxin (TTX) and atropine (P less than 0.05). Substance P-induced pyloric contractions were TTX sensitive (P less than 0.05) but were unaffected by atropine. We concluded that 1) length-tension properties of gastric muscle are similar and distinct from the pylorus and that 2) neuropeptide efficacy varies regionally within the feline stomach and within the pylorus.

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