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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 328 (1985), S. 446-453 
    ISSN: 1432-1912
    Keywords: Substance P ; Enteric neurons ; Autonomic nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The sites of action and possible roles of substance P in contracting the circular muscle of the guinea-pig ileum were studied using two analogues of substance P that act as antagonists of some of its actions. These ared-Arg1,d-Pro2,d-Trp7,9, Leu11-substance P andd-Pro2,d-Trp7,9-substance P, referred to by the single letter amino acid codes for the substituting amino acids as (RPWWL)-SP and (PWW)-SP, respectively. Records of circular muscle activity were taken from strips of intestine free of mucosa and submucosa and from rings with all layers of intestine intact. Substance P was equally effective in contracting the circular muscle strips as it was in contracting the longitudinal muscle. The contractions of strips were not blocked by hyoscine (2×10−6 M) or tetrodotoxin (6×10−7 M), but were substantially reduced by (RPWWL)-SP (6.7×10−6 M) or (PWW)-SP (2×10−5 M). In contrast, contractions of the circular muscle of whole rings of intestine elicited by low concentrations of substance P (4×10−7M) were blocked by hyoscine or tetrodotoxin but notreduced by the substance P antagonists in the concentrations referred to above. These observations indicate that the antagonists are effective at receptors for substance P on the muscle, but not at substance P receptors on enteric cholinergic nerves. Transmural stimulation of strips of circular muscle or of intestinal rings in the presence of hyoscine evoked contractions that were blocked by tetrodotoxin. These hyoscineresistant, nerve-mediated contractions could be elicited by single pulses in the strips. The contractions were reduced to less than 20% of original amplitude by (RPWWL)-SP (6.7×10−6M). Reflex contractions of the circular muscle recorded on the oral side of a distension stimulus had a low-threshold, hyoscine-sensitive and a high-threshold, hyoscine-insensitive, component. The low threshold component was unaffected by the substance P antagonists whereas the high threshold component was depressed. It is concluded that substance P nerves are effective in transmitting to the circular muscle, that they are final nerves in non-cholinergic excitatory reflexes, and that the substance P antagonist analogues can be used to distinguish actions of substance P at neural and muscle receptors.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 329 (1985), S. 382-387 
    ISSN: 1432-1912
    Keywords: Substance P ; Enteric neurons ; Mucosal transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The action of substance P (SP) on mucosal ion transport has been investigated in the guinea-pig small intestine. Segments of intestine were dissected free of external muscle and myenteric plexus and mounted in Ussing chambers. Short-circuit current (I sc) was measured as an indication of net ion transport across the tissue. SP (〉10−10 M) added to the submucosal side of the tissue caused a transient increase in I sc. Tetrodotoxin (TTX, 10−7 M) decreased the maximum SP response to 11% of the control value. TTX completely inhibited the response to electrical field stimulation but had no effect on I sc increases due to carbachol or theophylline. In the presence of hyoscine (10−7 M) the SP response was reduced to 42% of the control value, but hyoscine had no effect on the TTX-resistant SP response. Mepyramine (10−6 M) had no significant effect on the SP response. These results suggest that SP alters mucosal ion transport by stimulation of cholinergic and non-cholinergic nerves in the mucosa-submucosa. A small part of the SP response appears to be due to a direct action on epithelial cells. The SP antagonist (d-Arg1, d-Pro2, d-Trp7.9, Leu11)-SP decreased the magnitude of the TTX-resistant SP response, and caused a decrease of similar magnitude in the total SP response. These results imply that the major component of the SP response, which is due to an action on neurons, is unaffected by this antagonist. It is concluded that the SP receptors on epithelial cells are blocked by the antagonist and are different to the SP receptors on submucous neurons, which are not blocked by the antagonist.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 331 (1985), S. 260-266 
    ISSN: 1432-1912
    Keywords: Enteric neurons ; Serotonin ; Mucosal transport ; Substance P receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It is known that the majority of the mucosal nerve fibres in the guinea-pig small intestine arise from submucous ganglia. There are a number of neurochemically distinct populations of nerve cells in these ganglia, approximately half of them being cholinergic. In these studies we have stimulated isolated preparations of mucosa and submucosa with electrical field stimulation (EFS), 5-hydroxytryptamine (5-HT) and the nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium (DMPP) and monitored changes in ion transport. Segments of intestine were dissected free of external muscle and myenteric plexus and mounted in Ussing chambers. Short-circuit current (I sc) was measured as an indication of net ion transport across the tissue. EFS consisted of passing bipolar rectangular stimulus pulses through two platinum wires, one placed on each of the mucosal and submucosal sides of the tissue. EFS, 5-HT and DMPP each caused a transient increase inI sc. Tetrodotoxin (TTX) abolished all of the EFS response and the majority of the response observed with 5-HT or DMPP, suggesting that the action of these stimuli on the mucosa is primarily nerve-mediated. The TTX-sensitive responses to 5-HT (〉5×10−7 M) and DMPP consisted of two components, appearing with different latencies. The response to EFS also consisted of two components. Hyoscine abolished the first component of each of these responses and significantly reduced the amplitude of the second, by 40% (for EFS and 5-HT) and 84% (for DMPP). At lower 5-HT concentrations, only the later component was seen, and this was unaffected by hyoscine. These results suggest that the early component of each response is due to the release of acetylcholine from cholinergic nerves. The hyoscine-resistant responses to EFS and DMPP were reduced by a substance P antagonist (d-Arg1,d-Pro2,d-Trp7,9, Leu11), suggesting that these responses involve activation of substance P receptors in the mucosa. The studies suggest that EFS and 5-HT (〉5×10−7 M) stimulate both cholinergic and non-cholinergic nerves effectively, that 5-HT (10−8–5×10−7 M) preferentially stimulates non-cholinergic nerves and that DMPP preferentially stimulates cholinergic nerves.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 349 (1994), S. 455-462 
    ISSN: 1432-1912
    Keywords: 5-HT receptors ; Guinea-pig colon ; Longitudinal muscle ; Tachykinins ; Enteric neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A range of agonists and antagonists were used to characterize the receptors through which 5-hydroxytryptamine (5-HT) contracts and relaxes the longitudinal muscle of segments of guinea-pig distal colon, in vitro. 5-HT contracted the longitudinal muscle over the concentration range 10−9 to 10−4 mol/l. The 5-HT3 receptor agonist, 2-methyl-5-HT, produced concentration dependent contractions over the range 10−6 to 10−4 mol/l. 5-methoxytryptamine, an agonist at 5-HT4 receptors, caused contractions over a concentration range of 10−8 to 10−4 mol/l. The 5-HT4 antagonist, SDZ 205-557 (5 × 10−7 mol/l) substantially suppressed the responses to low concentrations of 5-HT and to 5-methoxytryptamine, but had no effect on the responses to higher concentrations of 5-HT. In contrast, the 5-HT3 antagonist, granisetron (10−6 mol/l), blocked the effect of 2-methyl-5-HT and substantially depressed responses to high concentrations of 5-HT, but had no effect on lower concentrations of 5-HT. Granisetron produced a small reduction in the response to 5-methoxytryptamine. Tetrodotoxin (TTX) (3 × 10−7 mol/l) almost abolished the response to 5-methoxytryptamine and markedly suppressed the response to 2-methyl-5-HT, but the responses to 5-HT were only partially reduced. The 5-HT, antagonist, methiothepin 10−6 mol/l. depressed the response to 5-HT 10−7 to 10−4 mol/l. and blocked its TTX insensitive component. The 5-HT2 antagonist, ketanserin, in concentrations up to 10−5 mol/l, had no effect on the contractions evoked by 5-HT. The response to 5-HT was substantially depressed by hyoscine (3 × 10−6 mol/l. The tachykinin antagonist, spantide 10−5 mol/l. depressed the response to 5-HT but to a lesser extent than hyoscine. Spantide and hyoscine combined completely blocked the contractile responses to 5-HT Responses to 2-methyl-5-HT were partially suppressed by hyoscine (3 x 10−6 mol/l. and spantide (10−5 mol/l) and completely blocked when both byoscine and spantide were present. Contractions evoked by 5-methoxytryptamine were partially blocked by hyoscine (3 × 10−6 mol/l) and were unaffected by spantide (10−5 mol/l), but a combination of hyoscine and spantide completely blocked such responses. When the excitatory transmission was blocked with hyoscine (3 × 10−6 mol/l) and spantide 10−5 mol/l) and the tone of the muscle raised, an inhibitory response to 5-HT was revealed that had a threshold concentration between 10−7 mol/l) and 3 × 10−7 mol/l, and a maximum effect at 10−4 mol/l. It was blocked by TTX (3 × 10−7 mol/l) and granisetron 10−6 mol/l. while N-nitro-l-arginine (NOLA) (10−4 mol/l) and SDZ 205-557 (5 × 10−7 mol/l) had no effect. Apamin A 10−6 mol/l. partially suppressed this response. It is concluded that 5-HT3, 5-HT4 and 5-HT1-like receptors mediate contraction of the longitudinal muscle of the distal colon. The 5-HT3 and 5-HT4 receptors are located on the excitatory motor neurons innervating the longitudinal muscle and the 5-HT1-like receptor is located on the muscle. 5-HT3 receptors are also found on inhibitory neurons to the muscle.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 333 (1986), S. 393-399 
    ISSN: 1432-1912
    Keywords: Enteric neurons ; Mucosal transport ; Noradrenaline ; Somatostatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Noradrenaline (NA) and somatostatin (SOM) stimulate intestinal water and ion absorption and are found in mucosal nerve fibres and nerve terminals in submucous ganglia of the guinea-pig small intestine. As the main projection of submucous neurons is to the mucosa, NA and SOM might alter mucosal transport either by a direct effect on the epithelium or indirectly, by affecting submucous neurons. In this study these two possible sites of action of NA and SOM have been investigated in mucosa-submucosa preparations of guinea-pig ileum. In addition, the actions of NA and SOM on the secretory responses caused by stimulation of different populations of submucous neurons have been studied. The stimulants of secretion used were a nicotinic agonist, 1,1-dimethyl-4-phenylpiperazinium (DMPP, 10−5 M), 5-hydroxytryptamine (5-HT, 10−7 M) and electrical field stimulation (EFS), which activate cholinergic, noncholinergic and mixed populations of submucous secretomotor neurons, respectively. Segments of intestine were dissected free of external muscle and myenteric plexus and mounted in Ussing chambers. Short-circuit current (I sc) was measured as an indication of net active ion transport across the tissue. NA (≥10−8 M) and SOM (〉10−10 M) each caused a decrease in I sc, indicating a net increase in ion absorption. The NA response was abolished and the magnitude of the SOM response was reduced to 20% by tetrodotoxin (10−7 M). DMPP, 5-HT and EFS each stimulated nerves that increased I sc and each of these responses was significantly diminished by NA and SOM; for both NA and SOM the decrease in the DMPP response was significantly greater than the decrease observed in the response to carbachol (10−6 M). Phentolamine (10−6 M) abolished all of the effects of NA but caused no change in the SOM effects. These studies have shown that NA and SOM cause similar changes in net ion transport, that their actions are primarily on submucous secretomotor neurons and that NA and SOM can diminish the responses to stimulation of both cholinergic and noncholinergic submucous neurons. In this tissue it is also known that SOM coexists with NA in noradrenergic nerve terminals in the submucosa. However, when applied together, NA and SOM caused no greater decrement in the carbachol and 5-HT responses than would be predicted by adding the separate effects of NA and SOM. Hence there was no obvious interaction between NA and SOM effects on mucosal transport.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 280 (1995), S. 549-560 
    ISSN: 1432-0878
    Keywords: Key words: Enteric nervous system ; Immunocytochemistry ; Calretinin ; Calbindin ; Bombesin ; Small intestine ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Light- and electron-microscopic studies were used to investigate connections between specific subgroups of neurons in the myenteric plexus of the guinea-pig small intestine. Inputs to two classes of calretinin-immunoreactive (IR) nerve cells, longitudinal muscle motor neurons and ascending interneurons, were examined. Inputs from calbindin-IR primary sensory neurons and from three classes of descending interneurons were studied. Electron-microscopic analysis showed that calbindin-IR axons formed two types of inputs, synapses and close contacts, on calretinin-IR neurons. About 40% of inputs to the longitudinal muscle motor neurons and 70% to ascending interneurons were calbindin-IR. Approximately 50% of longitudinal muscle motor neurons were surrounded by bombesin-IR dense pericellular baskets and 40% by closely apposed varicosities. At the electron-microscope level, the bombesin-IR varicosities were found to form synapses and close contacts with the motor neurons. Dense pericellular baskets with bombesin-IR surrounded 36% of all ascending interneurons, and a further 17% had closely apposed varicosities. Somatostatin- and 5-HT-IR descending interneurons provided no dense pericellular baskets to calretinin-IR nerve cells. Thus, calretinin-IR, longitudinal muscle motor neurons and ascending interneurons receive direct synaptic inputs from intrinsic primary sensory neurons and from non-cholinergic, bombesin-IR, descending interneurons.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 271 (1993), S. 333-339 
    ISSN: 1432-0878
    Keywords: Enteric nervous system ; Prevertebral ganglia ; Retrograde tracing ; Calbindin ; Vasoactive intestinal peptide (VIP) ; Intestine ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Retrograde tracing, using Fast Blue dye, was employed to determine the distribution of enteric nerve cells that project to the superior mesenteric and inferior mesenteric ganglia of the guinea-pig. Retrogradely labelled neurons were found in the myenteric but not submucous ganglia. When the superior mesenteric ganglion was injected, labelled neurons were found in low frequencies (less than 5 nerve cell bodies/cm2) in the duodenum, jejunum, ileum, caecum and proximal colon. The distal colon was analysed in five segments of equal length (1–5; oral to anal). Segment 1 had about 4 labelled nerve cells/cm2, whereas segments 2 to 5 displayed an average of about 25 nerve cells/cm2. The rectum contained about 36 labelled neurons/cm2. After injection of the inferior mesenteric ganglia with Fast Blue, no labelled neurons were found in the duodenum, jejunum, ileum or caecum. No labelled cells were observed in the gallbladder. A small number of labelled cells occurred in the proximal colon and in segment 1 of the distal colon. The frequency of labelled cells increased markedly in the more anal regions of the distal colon, and reached a peak in the rectum (138 cells/cm2). Both nerve lesions and immersion of the cut nerve in Fast Blue solution showed that the superior mesenteric nerve carries the axons of neurons located in the middle distal colon to the superior mesenteric ganglion. Almost half of the neurons in the rectum that project to the inferior mesenteric ganglia do so via the hypogastric nerves. Of neurons that projected to the inferior or superior mesenteric ganglia from the colon or rectum, similar proportions (about 75–80%) showed immunoreactivity for calbindin or VIP. For each of the prevertebral ganglia (coeliac, superior mesenteric and inferior mesenteric) the great majority of peripheral inputs arise from the large intestine.
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  • 8
    ISSN: 1432-0878
    Keywords: Calbindin ; Enteric nervous system ; Intestine, small ; Sensory neurons ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of nerve cells with immunoreactivity for the calcium-binding protein, calbindin, has been studied in the small intestine of the guinea-pig, and the projections of these neurons have been analysed by tracing their processes and by examining the consequences of nerve lesions. The immunoreactive neurons were numerous in the myenteric ganglia; there were 3500±100 reactive nerve cells per cm2 of undistended intestine, which is 30% of all nerve cells. In contrast, reactive nerve cells were extremely rare in submucous ganglia. The myenteric nerve cells were oval in outline and gave rise to several long processes; this morphology corresponds to Dogiel's type-II classification. Processes from the cell bodies were traced through the circular muscle in perforating nerve fibre bundles. Other processes ran circumferentially in the myenteric plexus. Removal of the myenteric plexus, allowing time for subsequent fibre degeneration, showed that reactive nerve fibres in the submucous ganglia and mucosa came from the myenteric cell bodies. Operations to sever longitudinal or circumferential pathways in the myenteric plexus indicated that most reactive nerve terminals in myenteric ganglia arise from myenteric cell bodies whose processes run circumferentially for 1.5 mm, on average. It is deduced that the calbindin-reactive neurons are multipolar sensory neurons, with the sensitive processes in the mucosa and with other processes innervating neurons of the myenteric plexus.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 269 (1992), S. 119-132 
    ISSN: 1432-0878
    Keywords: Enteric nervous system ; Coeliac ganglion ; Retrograde tracing ; Calbindin ; Vasoactive intestinal peptide ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The digestive tract of the guinea-pig, from the esophagus to the rectum, was examined in detail to determine the distribution and relative abundances of neurons in these organs that project to the coeliac ganglion and the routes by which their axons reach the ganglion. A retrogradely transported neuronal marker, Fast Blue, was injected into the coeliac ganglion. The esophagus, stomach, gallbladder, pancreas, duodenum, small intestine, caecum, proximal colon, distal colon and rectum were analysed for labelled neurons. Retrogradely labelled neurons were found only in the myenteric plexus of these organs, and in the pancreas. No labelled neurons were found in the gallbladder or the fundus of the stomach, or in the submucous plexus of any region. A small number of labelled neurons was found in the gastric antrum. An increasing density of labelled neurons was found along the duodenum. Similarly, an increasing density of labelled neurons was found from proximal to distal along the jejuno-ileum. However, the greates densities of labelled neurons were in the large intestine. many labelled neurons were found in the caecum, including a high density underneath its taeniae. An increasing density of labelled neurons was found along the length of the proximal colon, and labelled neurons were found in the distal colon and rectum. In total, more labelled cell bodies occurred in the large intestine than in the small intestine. The routes taken by the axons of viscerofugal neurons were ascertained by lesioning the nerve bundles which accompany vessels supplying regions of the digestive tract. Viscerofugal neurons of the caecum project to the coeliac ganglion via the ileocaeco-colic nerves; neurons in the proximal colon project to the ganglion via the right colic nerves, and neurons in the distal colon project to the ganglion via the mid colic and intermesenteric nerves. Neurons in the rectum project to the coeliac ganglion via the intermesenteric nerves. These nerves (except for the intermesenterics) all join nerve bundles from the small intestine that follow the superior mesenteric artery. All viscerofugal neurons of the caecum were calbindin-immunoreactive (calb-IR) and 94% were immunoreactive for vasoactive intestinal peptide (VIP-IR). In the proximal colon, 49% of labelled neurons were calb-IR and 85% were VIP-IR. In the distal colon, 80% of labelled neurons were calb-IR and 71% were VIP-IR.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 280 (1995), S. 549-560 
    ISSN: 1432-0878
    Keywords: Enteric nervous system ; Immunocytochemistry ; Calretinin ; Calbindin ; Bombesin ; Small intestine ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Light- and electron-microscopic studies were used to investigate connections between specific subgroups of neurons in the myenteric plexus of the guineapig small intestine. Inputs to two classes of calretinin-immunoreactive (IR) nerve cells, longitudinal muscle motor neurons and ascending interneurons, were examined. Inputs from calbindin-IR primary sensory neurons and from three classes of descending interneurons were studied. Electron-microscopic analysis showed that calbindin-IR axons formed two types of inputs, synapses and close contacts, on calretinin-IR neurons. About 40% of inputs to the longitudinal muscle motor neurons and 70% to ascending interneurons were calbindin-IR. Approximately 50% of longitudinal muscle motor neurons were surrounded by bombesin-IR dense pericellular baskets and 40% by closely apposed varicosities. At the electron-microscope level, the bombesin-IR varicosities were found to form synapses and close contacts with the motor neurons. Dense pericellular baskets with bombesin-IR surrounded 36% of all ascending interneurons, and a further 17% had closely apposed varicosities. Somatostatin-and 5-HT-IR descending interneurons provided no dense pericellular baskets to calretinin-IR nerve cells. Thus, calretinin-IR, longitudinal muscle motor neurons and ascending interneurons receive direct synaptic inputs from intrinsic primary sensory neurons and from non-cholinergic, bombesin-IR, descending interneurons.
    Type of Medium: Electronic Resource
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