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PubMed1987

The source of the nerve fibres forming the deep muscular and circular muscle plexuses in the small intestine of the guinea-pig.

A quantitative ultrastructural study was made of the neurites forming the deep muscular and circular muscle plexuses of the guinea-pig small intestine following microsurgical lesions designed to interrupt intrinsic and extrinsic nerve pathways within the intestinal wall. Removal of a collar of longitudinal muscle with attached myenteric plexus from the circumference of a segment of small intestine resulted in the underlying circular muscle. The few surviving neurites in the deep muscular plexus and circular muscle disappeared completely from lesioned segments that were, in addition, extrinsically denervated surgically. These results indicate that the majority of nerve fibres in the deep muscular and circular muscle plexuses of the guinea-pig small intestine is intrinsic to the intestine and originates from nerve cell bodies located in the overlying myenteric plexus. At the light-microscopic level, nerve bundles were traced from the myenteric plexus to the circular muscle.

Animals↗

PubMed2006

High affinity choline transporter immunoreactivity in rat ileum myenteric nerves.

Recently, an antibody against the choline transporter (CHT), an essential molecule involved in ACh uptake, was used to label cholinergic nerves in the central nervous system; however, the enteric nervous system (ENS) was not examined. The present study localised CHT immunoreactivity (CHT-IR) within the rat ileum ENS and determined whether it colocalised with immunoreactivity for markers of cholinergic, tachykinergic and nitrergic circuitry. Segments of rat ileum were fixed, prepared for sectioning or whole-mounts and incubated with anti-CHT antisera followed by a fluorescent secondary antibody. Samples were double-labelled with antibodies to nitric oxide synthase, substance P (SP), common choline acetyltransferase (cChAT) and vesicular acetylcholine transporter (VAChT). CHT-IR was present in varicosities of nerve fibres in the myenteric plexus and muscle layers of rat ileum. In the myenteric ganglia, CHT-IR was found in nerve fibres and the cytoplasm of some nerve cell bodies. In the myenteric ganglia, no CHT/cChAT-immunoreactive neurons were present. A small number of CHT/SP-immunoreactive neurons and CHT/SP-immunoreactive nerve fibres clustered around unlabelled neurons. CHT-IR colocalised with VAChT-IR in the myenteric plexus but only half of the CHT-immunoreactive myenteric nerve fibres were VAChT-immunoreactive and half of VAChT-immunoreactive fibres were CHT-immunoreactive. In the circular muscle, 75% of CHT-immunoreactive fibres were VAChT-immunoreactive. Thus, the anti-CHT antiserum labels neurons and nerve fibres in the rat ENS. It does not label cholinergic cChAT-immunoreactive neurons, although it does immunostain cholinergic VAChT-immunoreactive nerve fibres and a population of nerves that are not VAChT-immunoreactive.

Animals↗

PubMed1985

[Met-enkephalin-Arg-Gly-Leu-like immunoreactivity-containing nerve elements in the guinea-pig intestine. An immunohistochemical study using whole mount preparations].

The localization and distribution of Met-enkephalin-Arg-Gly-Leu (Met-Enk-Arg-Gly-Leu)-like immunoreactivity in whole mount preparations of different layers of guinea-pig gut (duodenum, jejunum, ileum and proximal colon) were studied by Sternberger's indirect immunocytochemistry. Anti-Met-Enk-Arg-Gly-Leu serum used as the primary antiserum was raised in a rabbit against synthetic Met-Enk-Arg-Gly-Leu coupled to ascaris protein by the glutaraldehyde method. The results obtained were summarized as follows: In the intestinal wall of the guinea-pig, Met-Enk-Arg-Gly-Leu-like immunoreactivity was localized only in nerve elements of the enteric nervous system. In the myenteric plexus, many perikarya showed Met-Enk-Arg-Gly-Leu-like immunoreactivity. Immuno-positive nerve fibers showing varicose appearance were demonstrated not only in the myenteric plexus but also in the longitudinal muscle layer, in the circular muscle layer, in the deep muscular plexus, in the submucous plexus and in the muscularis mucosae. No immuno-positive perikarya were found in the submucous plexus. Met-Enk-Arg-Gly-Leu-like immunoreactivity was not shown in the perivascular plexus and in the mucosa. Compared to those of the duodenum, jejunum or ileum, immuno-positive perikarya in the myenteric plexus of the proximal colon were apparently few in number. The density of a network in the deep muscular plexus formed by immunoreactive fibers was looser in the proximal colon than that in the duodenum, jejunum or ileum. Since Met-Enk-Arg-Gly-Leu-like immunoreactivity-containing nerve elements were densely distributed in the muscular layers of the intestinal wall, it is possible for this nervous system to regulate the contractility of the smooth muscles of the gut.

Animals↗

PubMed1995

Catecholamine-synthesizing enzymes in the rat stomach.

Local production of catecholamines in the stomach of the rat was studied by immunohistochemical demonstration of tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT), the enzymes catalyzing the formation of dopamine, noradrenaline and adrenaline, respectively. A rich innervation of TH- and DBH-immunoreactive nerve fibers was seen in the muscular layers and the myenteric plexus, in the submucosa and in the walls of submucosal blood vessels and in the lamina propria at the base of the epithelial layer. In addition, TH-, but not DBH-immunoreactive nerve fiber networks surrounding ganglion cells in the myenteric plexus were frequently observed, indicating dopaminergic preganglionic innervation of the myenteric plexus. In the oxyntic epithelium, single TH- and DBH-immunoreactive fibers extended in the strands of lamina propria as far as the middle portion of the gastric glands. A small population of single angulate cells in the oxyntic epithelium showed TH-, but not DBH-immunoreactivity. No specific PNMT immunoreactivity was observed.

Animals↗

PubMed1990

Evaluation of the activity of chemically identified enteric neurons through the histochemical demonstration of cytochrome oxidase.

The measurement of the density of the reaction product produced by the histochemical demonstration of cytochrome oxidase activity provides a method for the visual identification of physiologically active enteric neurons. The current study utilized the cytochrome oxidase technique in order to evaluate the metabolic history of neurons in different regions of the bowel and in chemically identified types of neuron. In addition, the effect of drugs or neurotoxins commonly used in the immunocytochemical identification of enteric neuronal phenotypes was also analyzed. Cytochrome oxidase activity was visualized with a blue-black reaction product resulting from the cobalt-intensified oxidation of 3,3'-diaminobenzidine. Peptides or 5-hydroxytryptamine (5-HT) were localized with biotinylated secondary antibodies and alkaline phosphatase-labeled avidin. Bound avidin or endogenous alkaline phosphatase was visualized with a red reaction product in the presence or absence, respectively, of levamisole. Use of measured without interference from a simultaneously demonstrated histo- or immunochemical marker. A multi-peptidergic class of cholinergic submucosal secretomotor neuron containing neuropeptide Y (NPY) and calcitonin gene related peptide (CGRP) immunoreactivities was found to be less metabolically active than the average of all submucosal neurons. In contrast, a non-cholinergic submucosal secretomotor neuron containing dynorphin (which is also known to contain vasoactive intestinal peptide) immunoreactivity was more metabolically active than submucosal neurons that do not contain this peptide. On average, submucosal neurons were more metabolically active than those of the myenteric plexus, and levels of metabolic activity in the myenteric plexus were found to be higher in the duodenum and the cecum than in the jejunum-ileum or colon. Myenteric neurons characterized by CGRP or NPY immunoreactivities or by endogenous alkaline phosphatase activity, were all less metabolically active than the average of all neurons in myenteric ganglia. Colchicine, which stimulates intestinal motility, was observed to increase cytochrome oxidase activity in enteric neurons, suggesting that an effect on the enteric nervous system contributes to its action on the bowel. The neurotoxins, 6-hydroxydopamine and 5,7-dihydroxytryptamine (5,7-DHT) were each found to stimulate neuronal metabolic activity. 5,7-DHT appeared to activate excitatory subtypes of 5-HT receptor since its effects were blocked or mimicked by compounds that act as antagonists or agonists, respectively, at these receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Alkaline Phosphatase↗

PubMed1977

The mechanism of action of narcotic analgesics in the guinea-pig ileum.

1. Intracellular recordings were made from neurones in the myenteric plexus of the guinea-pig ileum. Single myenteric ganglia were maintained in vitro and drugs were applied by adding them to the perfusing solution. 2. Narcotic analgesics hyperpolarized the membrane of a proportion of neurones in the myenteric plexus. 3. The membrane hyperpolarization was sometimes associated with a decrease in input resistance. These effects reduced the excitability of myenteric neurones. 4. The effects of narcotics occurred at low concentrations (10 nM to 1 micrometer), were stereospecific and were reversed by naloxone. 5. It is proposed that the morphine-sensitive neurones may be the cholinergic efferents to the muscle layers. By hyperpolarizing these neurones, morphine may prevent their excitation by electric field stimulation. This may explain why narcotic analgesics reduce the output of acetylcholine and the contractile response of this preparation when it is excited by field stimulation.

Action Potentials↗

PubMed1999

Regional differences in the sympathetic innervation of the guinea pig large intestine by neuropeptide Y- and tyrosine hydroxylase-immunoreactive nerves of divergent extrinsic origin.

Region-specific patterns of nerves with immunoreactivity to neuropeptide Y (NPY) have been described previously in the submucous plexus of guinea pig large intestine. Because these may have functional significance, the possibility of similar, characteristic variations of NPY-like immunoreactivity (NPY-ir) in the myenteric plexus was explored. Regional differences were found in the occurrence and pattern of distribution of NPY-ir in the myenteric plexus of the guinea pig large intestine. NPY-ir was present rarely within neuron somata in any region of the large intestine, and NPY-ir nerve fibers were present only within the distal large intestine, increasing progressively in density from the distal spiral to the rectum. Lesion of the colonic nerves, but not the hypogastric, intermesenteric, or lumbar splanchnic nerves, resulted in a loss of NPY-ir in the distal spiral and transverse colon but not in the descending colon or rectum. Ring myotomies in the descending colon resulted in a loss of NPY-ir proximal to the lesion. Dual-labeling immunohistochemical studies revealed that the NPY-ir nerve fibers rarely contained immunoreactivity for tyrosine hydroxylase (TH). Extrinsic nerve lesions resulted in an unequivocal reduction in NPY-ir in intraganglionic fibers of the submucosal plexuses of the transverse colon and a partial loss in the distal spiral and descending colon: the rectum was unaffected; in only a minority of guinea pigs, however, was any decrease in the NPY-ir innervation of submucosal blood vessels detected. The principal projections of NPY-ir nerves were from and through the inferior mesenteric ganglion; however, NPY-ir was not colocalized with TH-ir. It is proposed that nonnoradrenergic, NPY-containing neurons located in the inferior mesenteric ganglion project through the colonic nerves and that these proximally directed fibers innervate the transverse colon and the distal spiral. Nonnoradrenergic, NPY-ir neurons lying in the pelvic ganglia or sacral sympathetic chain may make an important contribution to the innervation of the myenteric plexus of the rectum and the descending colon.

Animals↗

PubMed1995

Effect on muscarinic acetylcholine receptors after experimental neuronal ablation in rat colon.

The etiology of denervation hypersensitivity was studied using a rat model. Degeneration of the myenteric plexus was produced by direct application of 0.1% benzalkonium chloride to the serosal surface of the distal colon. Thirty days later, the treated group was compared with a control group undergoing a sham operation. The treated group showed that the decreased number of ganglion cells of the myenteric plexus on routine stain and acetylcholinesterase staining demonstrated the myenteric plexus in the treated group diminished acetylcholinesterase activity. Methacholine (1%), a muscarinic agonist, increased intraluminal pressure in treated but not control rats. The dose-response curve of colonic muscle strips to oxotremorine showed a shift to the left, indicating greater sensitivity, in the treated bowel, with a 50% effective dose (ED50) of 2.5 x 10(-8) in treated muscle and 2.2 x 10(-7) in controls. Binding studies using [3H]quinuclidinyl benzilate ([3H]QNB) showed that the specific maximal binding (Bmax) for [3H]QNB was greater in treated than in untreated animals (228 +/- 26.1 and 135 +/- 42.9 fmol/mg protein, respectively; P < 0.01), even though the dissociation constants (Kd) were the same (0.398 +/- 0.083 and 0.406 +/- 0.065). These findings show that acquired denervation hypersensitivity in this model is due to an increase in the number of muscarinic acetylcholine receptors.

Animals↗

PubMed1995

Nitric oxide, an enteric nonadrenergic-noncholinergic relaxant transmitter: evidence using phosphodiesterase V and nitric oxide synthase inhibition.

1. The effects of NG-nitro-L-arginine (L-NOARG), a nitric oxide synthase inhibitor, and SK&F 96231, a phosphodiesterase type V inhibitor, on electrical field stimulated (EFS) nonadrenergic noncholinergic (NANC) relaxations of rat fundal strips, guinea-pig isolated ileum longitudinal muscle with intact myenteric plexus, and guinea-pig taenia caeci were investigated. 2. Reproducible repeated control random EFS frequency-response curves were obtained for all three tissues. 3. Depending on the frequency of stimulation, L-NOARG (10(-4)-5 x 10(-3) M) caused either a complete or partial inhibition of the NANC-induced relaxations of the rat fundal strips and the guinea-pig isolated ileum longitudinal muscle with intact myenteric plexus, but not of the guinea-pig taenia caeci. The inhibitory action of L-NOARG was partially or totally reversed, depending on the tissue, by L-arginine (5 x 10(-3) M). 4. SK&F 96231 (10(-6)-10(-4) M) caused a concentration- and frequency-dependent potentiation of both the size and duration of the EFS-induced NANC relaxant response of rat fundal strips and guinea-pig isolated ileum longitudinal muscle with intact myenteric plexus, but not of the guinea-pig taenia caeci. 5. Zaprinast, another phosphodiesterase type V inhibitor (10(-6)-10(-4) M) caused a concentration- and frequency-dependent potentiation of the NANC relaxant responses to EFS of rat fundal strips. 6. SK&F 96231 and zaprinast alone (10(-6)-10(-4) M) caused a concentration-dependent relaxation of the agonist-induced tone of all three tissues with the maximum degree of relaxation found to be in the order stomach < ileum < caecum. This is the reverse order for ability of SK&F 96231 to potentiate relaxant responses to EFS. 7. These results suggest NO is involved in the NANC nerve-mediated relaxation of rat fundal strips and guinea-pig isolated ileum longitudinal muscle with intact myenteric plexus, but not the guinea-pig taenia caeci.

Animals↗

PubMed2004

Calbindin-immunoreactive neurones in the ovine rumen.

In small laboratory animals, such as guinea pigs, immunoreactivity for the calcium-binding protein calbindin (CALB) can be used to distinguish functionally different classes of myenteric neurones. The rumen of sheep is a highly specialized gastrointestinal region, and the control of its functions requires specific intrinsic innervation patterns. The aim of this study was to neurochemically identify and characterize CALB-positive myenteric neurones of the ovine rumen. Therefore, we performed quadruple immunohistochemistry against CALB, substance P (SP), vasoactive intestinal peptide (VIP), and nitric oxide synthase (NOS) using whole-mount preparations of the ruminal myenteric plexus. On average, 3 +/- 2 and 1 +/- 0.4 myenteric neurones/ganglion were CALB-immunoreactive in suckling lambs and adult sheep, respectively. These neurones had Dogiel type-I morphology. Most of them (89.2% +/- 8.7% and 71.7% +/-44.8% in suckling lambs and adult sheep, respectively) did not colocalize any of the other antigenes. Since it has been shown in previous studies that ruminal myenteric neurones are immunoreactive for either choline acetyltransferase (ChAT) or NOS, we defined neurones which were CALB-positive and NOS-negative as CALB/ChAT. The other CALB-positive neurones were encoded CALB/NOS/+/-VIP (10.3% +/- 9.3% and 26.7% +/- 46.2% in suckling lambs and adult sheep, respectively) or CALB/ChAT/SP (0.5% +/- 1.0% and 1.7% +/- 1.9% in suckling lambs and adult sheep, respectively). We used cryostat sections of the ruminal wall to analyze the projections of the CALB-positive neurones. CALB-immunoreactive somata were exclusively located within the myenteric plexus. CALB-immunoreactive nerve fibers were found primarily in the lamina propria of the ruminal papillae. We conclude that CALB-positive myenteric neurones within the ovine rumen project to the epithelium; however, their functional role remains to be investigated.

Animals↗

PubMed1993

The effect of three dimensional collagen type I preparation on the structural organization of guinea pig enteric ganglia in culture.

In vivo, cellular relationships in the myenteric plexus are characterized by unusual compactness and by the arrangement of neurons and glia into ganglia and interconnecting strands. These features are lost when the myenteric plexus is placed in culture. In the present paper we test whether collagen type I, a major component of the matrix that surrounds the plexus in vivo, might have a role in maintaining normal neuron-glia relationships in this system. We report that a three-dimensional gel of rat tail collagen prevented the disaggregation of the guinea pig myenteric plexus in culture and induced the formation of a compact plexus-like cellular network when applied to disaggregated plexus cultures. These effects were not observed with soluble collagen. Immunohistochemical evidence was also obtained for synthesis of type I collagen by enteric glia. These observations indicate that type I collagen in a three-dimensional organization is capable of inducing and maintaining both the unusual compact organization of neurons and glial cells within myenteric ganglia and also the characteristic organization of these cells into an orderly network of ganglia and interconnecting strands.

Animals↗

PubMed1998

Regional and transmural density of interstitial cells of Cajal in human colon and rectum.

The interstitial cells of Cajal (ICC) are thought to play an important role in the control of gut motility. The regional and transmural pattern of distribution of ICC in the normal human colon and rectum was evaluated with immunohistochemistry using an anti-c-kit antibody. The transmural distribution of ICC was constant throughout the whole colon, the density of ICC was significantly greater at the myenteric plexus than at either the longitudinal or circular muscle layers, and in the rectum the transmural distribution was more even. Regionally, at the myenteric plexus, the transverse colon had a significantly greater density of ICC compared with the right colon (P = 0.038), left colon (P = 0.006), and rectum (P = 0.008). The pattern of distribution of ICC identified in this study is consistent with the proposed roles of ICC as colorectal pacemakers, intermediaries of the neural control of muscle activity, and coordinators of colorectal muscle activity. The highest density of ICC was at the myenteric plexus of the transverse colon, which is the proposed region of pacemaking activity.

Adult↗

PubMed1997

Intestinal pacemaker C-KIT+ cells and synapses in allied Hirschsprung's disorders.

The cause of bowel dysmotility in allied Hirschsprung's disorders (AHDs) such as hypoganglionosis (HYPG), immature ganglia (IMG) and neuronal intestinal dysplasia (NID) remains unexplained. Recent experimental studies in mice have shown that c-kit gene product positive (C-KIT+) cells are responsible for intestinal pacemaker activity and that c-kit is also closely involved in synapse formation. To further understand the pathophysiology of AHDs, the authors used immunohistochemistry to study the distribution of C-KIT+ cells and synapses in the muscle layers of normal bowel from controls (12 cases) and bowel from patients with AHDs (10 patients; mean age, 3.0 years; 5 HYPG, 3 NID, 2 IMG). Anti-human C-KIT serum and monoclonal antibody 171B5 (a novel marker of synapses) were used for visualization of C-KIT+ cells and 171B5+ synapses, respectively. In normal bowel from controls and patients with AHDs, moderate to many C-KIT immunoreactive (C-KIT-IR+) cells were observed in the muscle layers. Myenteric plexuses were clearly demarcated by C-KIT-IR+ cells. 171B5 immunoreactive (171B5-IR+) synapses were abundant in the muscle layers and within the myenteric plexuses. In contrast, the number of C-KIT-IR+ cells or 171 B5-IR+ synapses was reduced in the muscle layers of bowel affected by AHDs, except within the myenteric plexuses, where there was a moderate to large number of 171B5-IR+ synapses identified. A lack of intestinal pacemaker C-KIT+ cells may be of great significance with respect to the bowel dysmotility associated with AHDs and also to the abnormal synapse formation seen in the muscle layers of bowel affected by these disorders.

Adolescent↗

PubMed1991

Impaired sympathetic nerve function in the inflamed rat intestine.

The effect of intestinal inflammation on norepinephrine release from the myenteric plexus in the Trichinella spiralis-infected rat was assessed. Longitudinal muscle-myenteric plexus preparations were preincubated with [3H]norepinephrine and release was evoked by electrical field stimulation and KCl administration. Preincubation of preparations with desipramine or pretreatment of rats with 6-hydroxydopamine significantly suppressed the uptake and evoked release of [3H]norepinephrine; electrical field stimulation but not KCl-evoked release of [3H] norepinephrine was sensitive to tetrodotoxin. These results confirm the presence of functioning sympathetic nerves in the preparations. T. spiralis infection was associated with significant suppression of both electrical field stimulation and KCl-evoked release of [3H]norepinephrine on the sixth day postinfection, and the suppression persisted 100 days postinfection. No suppression of [3H]norepinephrine release was seen in the worm-free and noninflamed ileum of infected rats. Suppression of [3H]norepinephrine release from the jejunum of infected rats was attenuated by treatment with betamethasone (3.0 mg/kg SC daily). These results are consistent with the hypothesis that intestinal inflammation suppresses the release of norepinephrine from the myenteric plexus in the Trichinella-infected rat.

Animals↗

PubMed1995

Immunohistochemical study of the colonic muscle and innervation in idiopathic chronic constipation.

PURPOSE: This study was designed to investigate neural and muscular features of the colonic wall in patients with severe idiopathic constipation. METHODS: By using quantitative immunohistochemistry, resected specimens from 14 patients with idiopathic chronic constipation and 17 nonobstructed cancer controls were studied. RESULTS: Routine histology revealed no significant histologic abnormality throughout the colon apart from four cases of melanosis coli. Ratio of the thickness of circular to longitudinal muscle was significantly lower in the left colon in constipated subjects. The myenteric plexus appeared morphologically normal in all subjects. S-100 protein, which stains neuronal supporting tissues, demonstrated an increase in the proportion of neural tissue in the myenteric plexus. There was an increased number of PGP-9.5 immunoreactive nerve fibers in the muscularis propria in constipated patients, and this was significantly higher in the ascending and descending colon. CONCLUSION: Intractably constipated patients have alterations in the neural composition of the colonic myenteric plexus and innervation of the circular muscle.

Adolescent↗

PubMed1988

Polar innervation of enteric non-cholinergic and non-adrenergic neurons in the isolated guinea-pig ileum.

To study the polarity of the efferent pathway of the myenteric plexus, recordings were made of the mechanical activity of the longitudinal muscle of isolated guinea-pig ileal segments upon stimulation with an electrical field around the myenteric plexus contained within strips of longitudinal muscle (LM-MP) continuous with each end of ileal segment. The amplitude of the contractile response to stimulation of the anal LM-MP was always larger than that to the oral LM-MP. After cholinergic and adrenergic transmission was suppressed by atropine (10 microM) and guanethidine (1 microM), and the tone of the segment was enhanced by histamine (1 microM), the LM-MP stimulation produced non-cholinergic, non-adrenergic (NCNA) ascending contraction and NCNA descending relaxation. The NCNA contraction, but not the NCNA relaxation, was abolished or reduced by desensitization to substance P. The present results suggest that the NCNA innervation of the myenteric plexus participates in the polar effects observed in the guinea-pig ileum, that the NCNA excitatory response may be mediated at least in part by myenteric substance P neurons, and that the NCNA inhibitory response is mediated by non-adrenergic neurons.

Animals↗

PubMed1989

Influence of dopaminergic and noradrenergic systems on the release of opioid peptides in guinea-pig ileum.

Neuroleptic drugs increase the biosynthesis and release of opioid peptides from the myenteric plexus of guinea-pig ileum. In the present work, the involvement of dopamine receptors or alpha-adrenoceptors in the release of opioids from the myenteric plexus of guinea-pig was investigated. Acute or chronic treatment with prazosin, an alpha 1-blocking drug, produced no changes in the release of these peptides. Release was also unchanged after acute or chronic treatment with the alpha 2-blocking drug yohimbine. However, treatment with domperidone, a selective dopamine receptor antagonist, resulted in an increase in the release of opioids, as did treatment with (-)-3-(3-hydroxyphenyl)-N-n-propylpiperidine ((-)-3-PPP), a dopamine autoreceptor stimulant. It is concluded that the effect of neuroleptics on the release of opioids from myenteric plexus is due to the blockade of dopamine receptors, and that interruption of dopaminergic transmission produces an increase in opioid release at this level.

Adrenergic alpha-Antagonists↗

PubMed1982

Characterization of substance P-like immunoreactivity in peripheral sensory nerves and enteric nerves by high pressure liquid chromatography and radioimmunoassay.

Material exhibiting immunoreactivity for substance P in enteric nerves, obtained from the myenteric plexus of the guinea pig small intestine, and in the peripheral ends of sensory nerves of the ureter, atrium and superior mesenteric artery, was characterized by separation by high pressure liquid chromatography, and quantified by radioimmunoassay of fractions collected from the chromatograph. Capsaicin, which depletes substance P-like immunoreactivity from sensory, but not from other substance P-containing nerves, reduced the content of substance P-like immunoreactivity in ureter, atrium and superior mesenteric artery by more than 99.5%, whereas the reduction in immunoreactive material in the myenteric plexus was less than 10%. Separation of extracts of myenteric plexus, ureter and atrium on a reversed-phase column gave major peaks corresponding to authentic substance P and minor peaks that coeluted with oxidized substance P. If the extracts were oxidized with hydrogen peroxide before chromatography, all the immunoreactivity was found in the peak corresponding to oxidized substance P. In the superior mesenteric artery extracts, in addition to the components corresponding to substance P and its oxidized derivative, there was a small intermediate peak that has yet to be identified. Physalaemin, which has been suggested to be present in mammalian nerves, was not detectable in any of the extracts. It is concluded that both enteric nerves and the peripheral processes of sensory nerves which show immunoreactivity for substance P in this species contain the authentic peptide.

Animals↗