Biomedical subjects

J B Furness

Publications and source records attributed to J B Furness.

At least 145 records · Page 8Linked to original sources

PubMed1992

Light- and electron-microscopic immunochemical analysis of nerve fibre types innervating the taenia of the guinea-pig caecum.

The present work was undertaken to determine by immunocytochemical methods which of the putative enteric neurotransmitters are contained in axons supplying the guinea-pig taenia coli and what proportion of axons is accounted for by the presence of these substances. Numerous fibres displayed immunoreactivity for dynorphin (DYN), enkephalin (ENK), gamma-aminobutyric acid (GABA), nitric oxide synthase (NOS), substance P (SP) and vasoactive intestinal peptide (VIP), but, in contrast to other gut regions, fibres showing immunoreactivity for gastrin-releasing peptide, galanin and neuropeptide Y were rare in the taenia. Fibres reactive for calbindin, calcitonin gene-related peptide, cholecystokinin, 5-hydroxytryptamine and somatostatin were also rare. Tyrosine hydroxylase-like immunoreactivity (TH-LI) was present in numerous fibres that disappeared after extrinsic denervation, a procedure that did not detectably affect any of the other major groups of fibres. Simultaneous staining of extrinsically denervated preparations revealed that SP-LI and VIP-LI were located in separate fibres, and ultrastructural studies showed these to be 58% and 33% of intrinsic fibres supplying the muscle. Immunoreactivity for the general marker, neuron-specific enolase, was located in 95-98% of axons. ENK-LI and DYN-LI were in the same axons, and similar proportions of the fibres with either SP-LI or VIP-LI, about 85%, contained immunoreactivity for ENK and DYN. All VIP-LI fibres, but no SP-LI fibres, were reactive for NOS. The results imply that the taenia of the guinea-pig caecum is innervated by two major groups of enteric neurons: (i) excitatory neurons that contain ACh, SP, other tachykinins, and, in most cases, DYN-LI and ENK-LI; and (ii) inhibitory neurons that contain NOS-LI, VIP-LI, in most cases, the two opioids and, quite probably, ATP as a transmitter. GABA-LI is contained in a smaller population of intrinsic axons. Even though the taenia represents one of the simplest tissues for examining transmission from enteric neurons to intestinal muscle, it shares some of the complexity of other regions, in that four major axon types supply the muscle and both the enteric excitatory and enteric inhibitory neurons contain multiple transmitters.

Amino Acid Oxidoreductases↗

PubMed1992

Distribution of enteric nerve cells that project to the coeliac ganglion of the guinea-pig.

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 greatest 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.

Animals↗

PubMed1992

Post-stimulus depression of reflex changes in circular muscle activity in the guinea pig small intestine.

The extent and time course of depression of successive reflex responses recorded with intracellular microelectrodes from the circular smooth muscle of the guinea pig small intestine were determined. Two stimuli were used, distension and distortion of the mucosa by compression; these were applied either at the same or at different sites. Excitatory responses oral and inhibitory responses anal to the stimuli were recorded. Post-stimulus depression of both ascending excitatory and descending inhibitory reflexes occurred, but the extent of depression was slightly less for the descending inhibition. A conditioning distension lasting 9 s depressed the excitatory response to a test distension applied 2 s later at the same site by 90%. After 30 s the depression was 50% and test responses were normal if inter-stimulus intervals were increased to 2 min. Increasing the duration of the conditioning stimulus increased the depression. Post-stimulus depression was less for compression stimuli than for distension stimuli and prior mucosal compression had almost no effect on responses to subsequent distension. The post-stimulus depression was greater if conditioning and test stimuli were at the same rather than different sites. For different sites, conditioning stimuli at 15 mm from the recording site (near) depressed responses to stimuli at 30 mm (far) to a greater extent than far stimuli depressed responses to near stimuli. If the conditioning stimulus at 15 mm was maintained until after the far test stimulus was applied, depression of the test response did not occur. It is concluded that the major sites of post-stimulus depression are at the synapses between primary sensory neurons and the first interneurons of reflex pathways, and that post-stimulus depression also occurs at other places in the pathway, presumably at synapses between interneurons or between interneurons and motor neurons.

Animals↗

PubMed1992

Roles of peptides in transmission in the enteric nervous system.

Studies of the enteric nervous system have proved to be important in the development of new concepts of the chemical nature of transmission from neurons. In particular, they have revealed the multiplicity of influences that peptides can have on transmission, such as their action as primary transmitters, and the fact that they often act as co-transmitters in enteric neurons. However, in other cases no roles can be attributed to neuropeptides in enteric neurons, and their involvement in short-term changes in excitability seems minor.

Animals↗

PubMed1992

Distribution of peptide-containing nerve fibers in the gastric musculature of patients undergoing surgery for gastroesophageal reflux.

The distribution of nerve fibers and cell bodies reactive for the peptides enkephalin, neuropeptide Y, substance P, and vasoactive intestinal peptide were studied in biopsies of external muscle taken from the gastric body and antrum of 17 patients undergoing surgery for gastroesophageal reflux, and in regions of healthy stomach resected as part of gastric cancer operations. The results were correlated with preoperative measurements of liquid and solid emptying from the stomach in the patients with gastro-esophageal reflux. In three cases, no delay was detected in either liquid or solid emptying, and the distribution of peptide immunoreactive fibers in the external muscle was similar to that of healthy muscle. In 14 cases, the emptying of either liquids or solids or both was delayed, and in eight of these clearcut changes in the distribution of peptide-immunoreactive fibers occurred. In six cases, the number of enkephalin-immunoreactive fibers was fewer than normal in the biopsy from the gastric body (in one of these samples the number of substance P-immunoreactive fibers was also reduced). In another cae, the number of substance P-immunoreactive fibers in the antrum was reduced, and in another the number of vasoactive intestinal peptide and neuropeptide Y-immunoreactive fibers in the antral biopsy was reduced. It is concluded that in patients with gastroesophageal reflux who have delayed gastric emptying, a proportion demonstrate abnormalities of the peptide-immunoreactive fibers that innervate the gastric external muscle.

Enkephalins↗

PubMed1992

Nitric oxide synthase immunoactivity and NADPH diaphorase enzyme activity in neurons of the gastrointestinal tract of the toad, Bufo marinus.

The presence of nitric oxide synthase (NOS) was demonstrated immunohistochemically, and NADPH diaphorase was demonstrated by enzyme histochemistry in neurons throughout the gastrointestinal tract of the anuran amphibian, Bufo marinus. Successive staining showed that NOS immunoreactivity and NADPH diaphorase activity occurred in precisely the same subgroup of enteric neurons. Subsequent detailed studies of the distribution of these neurons were made using NADPH diaphorase histochemistry. Numerous reactive nerve cell bodies and fibres were found in the myenteric plexus from the esophagus to the cloaca. A dense innervation of the longitudinal and circular muscle layers occurred throughout the gastrointestinal tract. The lamina muscularis mucosae was only prominent in the stomach, where it was sparsely innervated. Reactive nerve cell bodies were common in the submucosa of the large intestine, less common in the small intestine and extremely rare in the stomach and esophagus. Reactive fibres contributed to subepithelial plexuses in the esophagus, colon, rectum and cloaca. It is concluded that NOS/NADPH diaphorase is conserved amongst vertebrate classes and that NO is a likely neurotransmitter in the toad gastrointestinal tract.

Amino Acid Oxidoreductases↗

PubMed1992

Convergence of reflex pathways excited by distension and mechanical stimulation of the mucosa onto the same myenteric neurons of the guinea pig small intestine.

The effects on morphologically and electrophysiologically characterized myenteric neurons of activation of intestinal reflex pathways were examined in vitro. Opened segments of guinea pig small intestine were pinned serosa down in an organ bath that had two balloons set into its base. A 5-10-mm-wide strip of myenteric plexus between the balloons was exposed from the mucosal side, and neurons were impaled with microelectrodes. Reflex pathways were stimulated by inflation of the balloons to distend the intestinal wall, and by deforming the exposed mucosal villi with a brush. Impaled neurons were classified electrophysiologically as AH-neurons or S-neurons (Hirst et al., 1974) and were injected with biocytin to determine their shapes and projections. None of the 58 AH-neurons responded to distension. In contrast, 63 of 131 S-neurons responded to distension with a burst of fast EPSPs; about one-third of the responding S-neurons received input from ascending reflex pathways, one-third received input from descending reflex pathways, and one-third received input from both ascending and descending pathways. Most neurons in this last group supplied extensive varicose branches to the tertiary plexus and were probably longitudinal muscle motor neurons. Neurons receiving input from only one pathway usually projected in the direction of that pathway; many of these were circular muscle motor neurons. Almost all neurons responding to distension were also excited by deforming the villi. Responses evoked by distension or deforming the mucosa declined when stimuli were repeated at intervals less than 10 sec. This was seen in ascending and descending pathways but was more prominent in the former. Deforming the mucosa evoked a normal response even when the response to repeated distensions had disappeared. It is concluded that distension and deforming the mucosa excite separate populations of sensory neurons to activate reflex pathways that converge onto common motor neurons and probably onto common interneurons.

Animals↗

PubMed1991

Ramifications of the axons of AH-neurons injected with the intracellular marker biocytin in the myenteric plexus of the guinea pig small intestine.

The projections and terminal ramifications of electrophysiologically characterized myenteric neurons of the guinea pig small intestine were studied after intracellular injection of the marker substance biocytin. Myenteric neurons were impaled with microelectrodes containing 4% biocytin in 2 M KCl (pH 7.4) and characterized electrophysiologically as either AH-neurons or S-neurons. AH-neurons were neurons in which action potentials were followed by prolonged after-hyperpolarizations (lasting greater than 4 seconds). S-neurons were neurons in which such hyperpolarizations were not seen. Electrical stimulation of internodal strands evoked prominent fast excitatory synaptic potentials in S-neurons, but not in AH-neurons. Biocytin was injected electrophoretically into the impaled AH-neurons by passage of hyperpolarizing current (0.6-0.8 nA for 5-15 minutes) through the recording electrode. The preparation was then fixed in Zamboni's fixative, dehydrated, and exposed to avidin coupled to horseradish peroxidase which allowed the injected biocytin to be visualised via a diaminobenzidine reaction. In many cases, the injected biocytin appeared to fill all the processes of injected AH-neurons that ramified within the myenteric plexus. The filled processes included axons running up to 4 mm within the plexus and profuse varicose terminals ramifying within both the ganglion containing the injected cell body and nearby ganglia. Most (90%) cell bodies of the injected AH-neurons had the morphology of Dogiel type II neurons; large, mostly smooth cell bodies with few short processes and several long processes. The other 10% of the AH-neurons had similar cell bodies and long processes but also had prominent short filamentous processes. This population was termed dendritic AH-neurons. The projections and terminals of 28 AH/Dogiel type II neurons and 7 dendritic AH-neurons were analysed in detail. Both types of neurons project circumferentially to provide terminals to nearby ganglia, but the AH/Dogiel type II neurons also provide terminals to their own ganglia while the dendritic AH-neurons typically do not. Although many of the injected AH-neurons had projections orally or anally along the intestine no evidence for a preferential direction of projection was obtained. Analysis of the areas and distributions of the terminal fields of the AH/Dogiel type II neurons suggests that each may contact several other myenteric neurons and that each myenteric neuron may receive input from about ten AH/Dogiel type II neurons.

Action Potentials↗

PubMed1991

Evidence that nitric oxide participates in non-adrenergic inhibitory transmission to intestinal muscle in the guinea-pig.

The possible involvement of nitric oxide (NO) in non-adrenergic nerve-mediated relaxations of guinea-pig gastrointestinal smooth muscle was investigated using longitudinal muscle that lies between the taenia of the caecum. Relaxations induced by electrical field stimulation in this preparation are similar to those described in other preparations of guinea-pig intestinal muscle when enteric inhibitory neurons are stimulated; they were blocked by tetrodotoxin (10(-6) M) but were unaffected by guanethidine (10(-6) M). N-Nitro-L-arginine (NOLA) (5 x 10(-5) to 10(-4) M), an inhibitor of NO synthase, and haemoglobin (10(-5) M), which reduces bioavailability of NO, both reduced the amplitude of nerve-mediated relaxations to less than 50%, without affecting the ability of the muscle to relax. These results suggest that NO may play a role in inhibitory neurotransmission to this preparation.

Animals↗

PubMed1991

Marsupial possum neurotensin: a unique mammalian regulatory peptide exhibiting structural homology to the avian analogue.

Neurotensin has been isolated from small intestinal extracts of an Australian marsupial, the brush-tailed possum (Trichosurus vulpecula). The primary structure was determined as: pGlu-Leu-His-Val-Asn-Lys-Ala-Arg-Arg-Val-Tyr-Ile-Leu. When compared with bovine neurotensin, marsupial possum neurotensin exhibits four amino acid substitutions. His for Tyr3, Val for Glu4 and Ala for Pro7 are identical with those found in chicken neurotensin. In addition, substitution of Pro10 with Val is unique among all neurotensins sequenced to date. Marsupial possum neurotensin is therefore of unique primary structure, displaying most sequence homology with its avian counterpart. This neurotensin may thus resemble the phylogenetic precursor present at the time of divergence of primitive mammals and birds.

Amino Acid Sequence↗

PubMed1991

Interactions between reflexes evoked by distension and mucosal stimulation: electrophysiological studies of guinea-pig ileum.

Intracellular recording methods were used to examine stereotyped reflexes evoked in the circular muscle of guinea-pig small intestine by distension or repetitive deformation of the mucosal villi, in vitro. Both stimuli evoked compound excitatory junction potentials (EJPs) on the oral side of the site of stimulation and compound inhibitory junction potentials (IJPs) on the anal side. Stimulation of the mucosa by application of 10 microliters of 0.5 M HCl evoked similar reflex responses in the circular muscle. The compound EJPs evoked by mucosal stimulation were depressed, but not abolished, by 1 microM hyoscine, indicating that these responses were partially mediated by release of acetylcholine, as are the equivalent responses evoked by distension. The compound EJPs and the compound IJPs evoked by maintained distension or by repeated mechanical stimulation of the mucosa were transient, lasting in most cases for 3-5 s before the membrane potential returned to resting level. This decline (rundown) occurred in part of the circuit close to the site of stimulation as stimuli applied elsewhere during the period of rundown evoked normal EJPs and IJPs. Mechanical stimuli (brush strokes that deformed the mucosal villi) applied to the mucosa at the site of a maintained distension evoked responses of normal amplitude during the period when the response to the distension had declined to zero. In contrast, during the period when the responses to repetitive mechanical stimulation of the mucosa had disappeared, the reflex responses evoked by distension at the same site were substantially augmented. Chemical stimulation of the mucosa with acid also enhanced the responses to distension.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Evidence that myenteric neurons of the gastric corpus project to both the mucosa and the external muscle: myectomy operations on the canine stomach.

The distribution of nerve cell bodies and fibres in the canine stomach was investigated using antibodies to the general neuronal marker, neuron-specific enolase. Prominent ganglia containing many reactive nerve cells were found in the myenteric plexus of the gastric corpus and antrum. Nerve cells were absent from the submucosa of the corpus and were extremely rare in the antrum. Removal of areas of longitudinal muscle and myenteric plexus from the corpus (myectomy), with 7 days allowed for axon degeneration, resulted in the loss of fibres reactive for galanin, gastrin-releasing peptide, substance P and vasoactive intestinal peptide from both the circular muscle and mucosa in the area covered by the lesion. Combined vagotomy and sympathetic denervation did not significantly affect these fibres, but did cause fibres reactive for calcitonin gene-related peptide to degenerate. It is concluded that the myenteric plexus of the gastric corpus, like the myenteric plexus of the small intestine and colon, is the source of nerve fibres innervating the circular muscle, but, in contrast to other regions of the gastrointestinal tract, myenteric ganglia, not submucous ganglia, are the major, or sole, source of the intrinsic innervation of the mucosa.

Animals↗

PubMed1991

Comparison of the presence and actions of substance P and neurokinin A in guinea-pig taenia coli.

The presence and sites of action of two closely related tachykinins, substance P (SP) and neurokinin A (NKA), were examined in the taenia coli of the guinea-pig. SP- and NKA-like immunoreactivity (LI) were demonstrated histochemically in nerve fibres supplying the taenia. Chromatographic characterization of aqueous acetic acid extracts of taenia showed only one peak of SP-LI, corresponding in retention time to authentic SP, whereas there were multiple peaks of NKA-LI, the major one of which corresponded to authentic NKA. SP-LI and NKA-LI, determined by radioimmunoassay, were in a molar ratio of SP equivalents to NKA equivalents of 8.5:1 in taenia extracts. Extrinsic denervation of the caecum had no significant effect on the concentration of either SP-LI or NKA-LI or on their immunohistochemical distributions. Both SP and NKA (10(-10) to 10(-5) M) caused contractions of the taenia that were unaffected by hyoscine (10(-6) M), mepyramine (10(-6) M) or tetrodotoxin (5 x 10(-7) M), indicating that both peptides act directly on the smooth muscle of the taenia. Contractions to SP occurred after a short, but concentration-dependent, delay, reached a peak quickly, and then decayed. In contrast, NKA caused contractions after longer latencies, the peak was reached more slowly, and the response was maintained for up to 10 min. (D-Pro2, D-Trp7,9)-SP (10(-5) M) antagonised responses to SP and NKA to a similar degree. It is concluded that both NKA and SP should be considered as transmitter candidates for non-cholinergic nerve-mediated excitation in the taenia.

Animals↗

PubMed1991

Calbindin-immunoreactive nerve terminals in the guinea pig coeliac ganglion originate from colonic nerve cells.

Previous work has shown that calbindin-immunoreactive (calbindin-IR) nerve terminals are numerous in guinea pig prevertebral ganglia. A high proportion of those colonic nerve cells that project to the inferior mesenteric ganglia are calbindin-IR, but none of the neurons that project from the small intestine to the coeliac ganglion are immunoreactive for calbindin. The present work was designed to determine the source of the calbindin-IR fibres and the pathways by which they reach the coeliac ganglion. Sections through the major nerve trunks that connect with the coeliac ganglion revealed numerous calbindin-IR fibres in the inferior coeliac nerves and in the intermesenteric nerves, while there were very few fibres in the splanchnic or superior coeliac nerves. When all peripheral nerve connections to a lobe of the coeliac ganglion were cut, all calbindin-IR terminals degenerated. Cutting the ileo-caeco-colic nerves caused a substantial reduction in the density of nerve fibres in the coeliac ganglion, whereas no significant reduction could be detected when the intermesenteric nerves were cut. However, lesion of both the ileo-caeco-colic and intermesenteric nerves caused all the calbindin-IR nerve fibres in the coeliac ganglion to degenerate. It is concluded that most or all of the calbindin-reactive nerve terminals in the coeliac ganglion originate from the large intestine and that most reach the ganglion via the ileo-caeco-colic nerves. Thus many colonic intestinofugal neurons, supplying both the coeliac and inferior mesenteric ganglia, are immunoreactive for calbindin, whereas small intestinal intestinofugal neurons are not immunoreactive for this protein.

Animals↗

PubMed1991

Mucosal distortion by compression elicits polarized reflexes and enhances responses of the circular muscle to distension in the small intestine.

The possibility that distortion of the mucosa by compression might be a sufficient stimulus to evoke reflex responses in intestinal muscle, and that such reflexes might summate with distension-evoked (stretch) reflexes, was tested in isolated segments of guinea pig small intestine. Opened segments of intestine were pinned flat in an organ bath with, or without, distending balloons embedded in its base. Intracellular microelectrode recordings were taken from the circular muscle oral and anal to sites of application of sensory stimuli. Pressure against the mucosa, which distorts the villi without the wall being stretched, evoked polarized reflex responses in the circular muscle, consisting of excitatory junction potentials oral and inhibitory junction potentials anal to the stimulus. Distension stimuli applied by 6-mm diameter balloons that pushed against either the serosal or the mucosal surface also evoked excitatory junction potentials in the muscle oral to the stimulus and inhibitory junction potentials at anal sites. Response amplitudes were 20% greater when the distending balloon pushed against the mucosal surface. Responses to distension from the serosal side were of 20% greater amplitude when combined with mucosal distortion by compression than without such compression. It is concluded that peristaltic movements that are commonly studied in the small intestine can be consequences of reflexes elicited at the same time from mucosal distortion receptors and from stretch receptors.

Animals↗

PubMed1991

Synaptic responses evoked by mechanical stimulation of the mucosa in morphologically characterized myenteric neurons of the guinea-pig ileum.

Recordings were made from myenteric neurons of the guinea-pig ileum during reflexes evoked by mechanical stimulation of the mucosa. Impaled neurons were injected with dye (Lucifer yellow or biocytin), and their shapes were determined. All neurons were 5-12 mm from the stimulus, a brush stroke that deformed the mucosal villi. Neurons were classified as S-neurons or AH-neurons (Hirst et al., 1974). About 40% of S-neurons oral to a stimulus responded with bursts of fast EPSPs (average frequency, 15-40 Hz); these neurons were in ascending reflex pathways. About 60% of S-neurons anal to a stimulus responded with similar bursts of fast EPSPs or slow depolarizations; these neurons were in descending pathways. Only 2 of 48 AH-neurons responded, both in descending pathways. Most S-neurons in either ascending or descending pathways received inputs from at least 2 or 3 other neurons. Action potentials evoked during a response averaged 3-10 Hz in frequency, with occasional bursts at up to 100 Hz. The speed of conduction along the reflex pathways was about 0.5 m/sec. All S-neurons were uniaxonal, but they differed in size, dendritic morphology, and projections. The axons of S-neurons injected with biocytin were followed up to 7 mm within the myenteric plexus. Three S-neurons projected to the tertiary plexus and were probably longitudinal muscle motor neurons; 2 of these were in descending pathways. Five S-neurons projected along the intestine and had varicose collaterals in some ganglia. These neurons were probably interneurons; 3 were descending and 2 ascending, and all responded in the appropriate reflex pathway. Many S-neurons had short axons that entered the circular muscle and were probably circular muscle motor neurons. Others projected several millimeters along the intestine before entering the circular muscle or fading beyond detection. From this study, we have been able to deduce the circuits mediating ascending and descending mucosa-to-muscle reflexes. It is concluded that AH-neurons are primary sensory neurons and S-neurons are interneurons and muscle motor neurons in the circuits.

Animals↗

PubMed1990

Calbindin immunoreactivity in sensory and autonomic ganglia in the guinea pig.

Immunoreactivity (IR) for the calcium binding protein, calbindin, was localized in sensory ganglia (nodose, trigeminal and dorsal root), in parasympathetic ganglia (otic and sphenopalatine) in sympathetic chain ganglia and in sympathetic pre-vertebral ganglia of guinea pig. In sensory ganglia, fine nerve fibres with calbindin-IR surrounded the majority of cell bodies, a low proportion of which were themselves reactive. In cranial parasympathetic and in sympathetic chain ganglia, a small proportion of nerve cells was surrounded with baskets of calbindin-IR nerve fibres, but very few cell bodies were reactive. In prevertebral sympathetic ganglia, dense networks of terminals surrounded many cell bodies, but few somata were themselves reactive. In the coeliac and inferior mesenteric ganglia, the calbindin-IR nerve fibres surrounded somatostatin-IR cell bodies, but not those with neuropeptide Y-IR. It is concluded that specific subgroups of peripheral autonomic and sensory neurones have calbindin-IR.

Animals↗

PubMed1990

An electrophysiological study of the projections of putative sensory neurons within the myenteric plexus of the guinea pig ileum.

Conduction of action potentials in the processes of AH (afterhyperpolarizing) neurons has been examined in the myenteric plexus of the guinea-pig small intestine. AH neurons are a morphologically distinct class of myenteric neurons in which the action potentials are followed by long lasting afterhyperpolarizations and which usually lack fast synaptic inputs. These neurons have large smooth cell bodies and several long processes. We have used electrophysiological methods, combined with intracellular injection of the fluorescent dye 5(6)-carboxyfluorescein, to examine the directions of projection and lengths of axons of AH neurons. AH neurons of the myenteric plexus projected circumferentially in both directions from the cell soma for electrophysiologically determined average distances of 0.74 +/- 0.05 mm. Thus, the neurons span about 1.5 mm of the circumference of the intestine. About one quarter of the AH neurons had one, or rarely two, processes that ran anally after initially projecting circumferentially. All processes conducted action potentials, with average conduction velocities of 0.23 +/- 0.02 ms-1.

Action Potentials↗