RESUMEN
REASONS FOR PERFORMING STUDY: Slow waves are rhythmic pacemaker currents generated by the gastrointestinal pacemaker cells, the interstitial cells of Cajal, and represent the rate-limiting step for small intestinal smooth muscle contractions. Therefore, factors that affect slow wave activity may also influence contractile activity. It is not known how temperature changes may influence slow wave activity in the horse. This could be of relevance during colic surgery if cooling of exposed intestine resulted in reduced slow wave activity potentially exacerbating post operative ileus. OBJECTIVES: To evaluate the effect of temperature changes on in vitro slow wave activity of normal equine ileum using intracellular recording techniques. STUDY DESIGN: In vitro experimental study. METHODS: A segment of ileum was collected immediately following euthanasia from 9 horses for reasons unrelated to the gastrointestinal tract. Intracellular recordings of membrane potentials were made from individual smooth muscle cells. The temperature of the tissue bath was altered during the course of each experiment across a range of 27-41°C. All data were recorded and stored using a computer-interfaced acquisition system. A software package was used to analyse slow wave frequency, duration, amplitude and resting membrane potential. RESULTS: In all 9 horses, slow wave frequency was highly temperature sensitive and approximately linearly related to the temperature over the range studied, increasing by 0.5 cycles/min for each 1°C increase in temperature (P<0.001). The initial slow wave frequency resumed when the temperature was returned to 37°C. The recovery time appeared to be directly related to the duration for which the temperature had been changed. CONCLUSIONS: Slow wave frequency in the equine ileum is highly temperature sensitive. As post operative ileus is a major cause of morbidity and mortality in the horse, the negative effect of lower temperatures on slow waves, and therefore contractile activity, should be considered.
Asunto(s)
Motilidad Gastrointestinal/fisiología , Caballos/fisiología , Íleon/fisiología , Temperatura , AnimalesRESUMEN
Intestinal motility disorders are an important problem in horses and donkeys and this study was carried out in order to evaluate the enteric neurons in animals with and without intestinal disease. Surplus intestinal tissue samples were collected from 28 horses undergoing exploratory laparotomy for colic. In addition, surplus intestinal samples from 17 control horses were collected immediately following humane destruction for clinical conditions not relating to the intestinal tract. Similar samples were also collected during routine post-mortem examinations from 12 aged donkeys; six animals were humanely destroyed for conditions related to the intestinal tract, while the remaining six were humanely destroyed for other reasons including dental and orthopaedic diseases. Tissue samples were fixed in formalin and immunohistochemical labelling was performed targeting the enteric neurons using a polyclonal antibody specific for the neuronal marker PGP 9.5. The distribution and density of neuronal networks were assessed qualitatively and semiquantitatively. There was strong PGP 9.5 expression in both the horse and donkey samples and labelling was detected throughout the tissue sections. In both species, PGP 9.5-immunoreactive nerve fibres were detected in all layers of the intestinal tract, both in large and small intestinal samples. Networks of enteric neurons were present in the donkey with a similar distribution to that seen in the horse. There was no demonstrable difference in enteric neuronal density and distribution in the groups of animals with intestinal disease compared with those without, apart from two (out of 28) horses with intestinal disease that showed a marked reduction in PGP 9.5 immunoreactivity. Apart from these two animals, this total cohort analysis differs from some previously observed findings in horses with intestinal disease and may therefore reflect the different pathophysiological processes occurring in varying intestinal conditions resulting in colic both in the donkey and the horse.
Asunto(s)
Sistema Nervioso Entérico/metabolismo , Enfermedades de los Caballos/metabolismo , Enfermedades Intestinales/veterinaria , Intestino Delgado/metabolismo , Neuronas/metabolismo , Ubiquitina Tiolesterasa/metabolismo , Animales , Cólico/metabolismo , Cólico/patología , Cólico/veterinaria , Sistema Nervioso Entérico/patología , Equidae , Enfermedades de los Caballos/patología , Caballos , Enfermedades Intestinales/metabolismo , Enfermedades Intestinales/patología , Intestino Delgado/patología , Neuronas/patologíaRESUMEN
REASONS FOR PERFORMING STUDY: The generation and maintenance of intestinal motility patterns involve the complex interactions of several components including the gastrointestinal pacemaker cells (interstitial cells of Cajal, ICC). Central to ICC function is the generation of rhythmic pacemaker currents, namely slow waves, which represent the rate limiting step for intestinal smooth muscle contractions. Currently, intracellular slow wave activity has not been demonstrated in the equine colon. OBJECTIVES: To characterise the in vitro myoelectrical activity of the equine pelvic flexure using intracellular recording techniques. METHODS: Intestinal samples were collected immediately following euthanasia from 14 normal horses. One millimetre thick tissue sections were pinned and superfused with warmed, oxygenated Krebs solution. Intracellular recordings were made from smooth muscle cells close to the submucosal border of the circular muscle layer. The L-type Ca(2+) channel blocker nifedipine was added to the superfusion fluid in 9 experiments while the Na(+) channel blocker tetrodotoxin was added to the superfusion fluid in 4 experiments. The data were recorded and stored using an acquisition system and a software package used to analyse the recordings. RESULTS: In 10 of the 14 horses, electrical events consistent with slow wave patterns were recorded from individual smooth muscle cells. Surprisingly, adding nifedipine to the superfusion fluid abolished all electrical activity. In contrast, tetrodotoxin had no apparent effect on the electrical activity. CONCLUSIONS: Assuming that the electrical events were slow waves, the blockade by nifedipine suggests significant and potentially important differences in the ionic mechanisms responsible for slow waves in the different regions of the equine intestinal tract, which deserve further evaluation.
Asunto(s)
Fenómenos Electrofisiológicos/fisiología , Caballos/fisiología , Intestinos/fisiología , Animales , Femenino , Motilidad Gastrointestinal/fisiología , MasculinoRESUMEN
Intestinal tissue samples were collected during routine post-mortem examinations from 12 aged donkeys. Six animals were euthanised due to impaction of the pelvic flexure of the large colon, while the remaining six were euthanised for non-enteric reasons such as dental or orthopaedic disease. Immunohistochemical labelling was performed to demonstrate the gastrointestinal pacemaker cells, the interstitial cells of Cajal (ICC), with polyclonal c-Kit antibodies. The distribution and density of the cellular networks were assessed qualitatively and semi-quantitatively. ICC networks are present in the donkey, with distribution similar to that of the horse, and they remain strongly immunoreactive in the older animal. There was no difference in the density and distribution of ICC in animals with or without intestinal disease.
Asunto(s)
Equidae/metabolismo , Células Intersticiales de Cajal/metabolismo , Enfermedades Intestinales/veterinaria , Proteínas Proto-Oncogénicas c-kit/metabolismo , Envejecimiento , Animales , Colon/metabolismo , Inmunohistoquímica , Enfermedades Intestinales/metabolismo , Proteínas Proto-Oncogénicas c-kit/genéticaRESUMEN
AIM: To identify the interstitial cells of Cajal in the porcine ileum for the first time immunohistochemically and to examine the electrical properties of intestinal smooth muscle in the same region. METHODS: In vitro intracellular microelectrode recordings were made from smooth muscle cells in cross-sectional preparations from abattoir-derived healthy porcine ileum. Immunohistochemical labelling of interstitial cells of Cajal was performed using an anti-Kit antibody. RESULTS: Slow waves were recorded in the circular muscle layer of all ileal preparations. The mean resting membrane potential of smooth muscle cells was -61.0 +/- 1.3 mV. Slow waves had a mean amplitude of 8.5 +/- 0.5 mV, a frequency of 9.9 +/- 0.1 cycles per minute and a duration of 5.6 +/- 0.1 s. A waxing and waning pattern of slow wave activity was occasionally observed. In addition, higher frequency spiking activity associated with contractions was observed in some recordings. The L-type calcium channel blocker nifedipine abolished both the spiking activity and the contractions, but had no significant effect on slow wave characteristics. Current-injection manipulation of the resting membrane potential had no effect on slow wave amplitude, frequency or duration. Kit-immunoreactive interstitial cells of Cajal were identified in the ileal samples and were present in the region of the myenteric plexus and in the circular and longitudinal muscle layers. CONCLUSION: This study recorded slow waves in vitro and demonstrated immunohistochemically the presence of interstitial cells of Cajal in the normal porcine ileum. This study forms a basis for future physiological and pathophysiological comparative studies of intestinal motility.
Asunto(s)
Íleon/citología , Íleon/fisiología , Músculo Liso/inervación , Músculo Liso/fisiología , Plexo Mientérico/fisiología , Animales , Bloqueadores de los Canales de Calcio/farmacología , Estimulación Eléctrica , Electrofisiología , Motilidad Gastrointestinal/fisiología , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Microelectrodos , Contracción Muscular/fisiología , Plexo Mientérico/citología , Nifedipino/farmacología , PorcinosRESUMEN
This paper describes the histopathological and immunohistochemical changes in the central, autonomic and enteric nervous systems in a well-documented case of equine dysautonomia (ED), after the animal had recovered without significant residual clinical signs. Evidence of neuronal degeneration, such as neuronal chromatolysis, glial scars or a decrease in density of neurons, was not observed in the midbrain, pons, medulla oblongata or spinal cord, including the nuclei of cranial nerves III, V, VII, X and XII. In addition, no evidence of muscle denervation or re-innervation, such as group atrophy of clusters of cells or grouping of cells of similar size in the triceps muscle, was observed. These findings support the hypothesis that the chromatolytic motor neurons may not progress to cell death in ED. The autonomic ganglia showed evidence of previous neuronal loss. In the myenteric and submucosal plexuses of the ileum there was significant loss of enteric neurons. However, in the ileum, a continuous network of interstitial cells of Cajal (ICC) was observed by means of immunohistochemical techniques. It is possible that recovery without significant residual clinical signs was associated with lack of damage to, or more likely recovery of, the ICC, which have a pacemaker function in the intestinal tract.
Asunto(s)
Enfermedades del Sistema Nervioso Autónomo/patología , Enfermedades del Sistema Nervioso Autónomo/veterinaria , Enfermedades de los Caballos/patología , Neuronas/patología , Animales , Enfermedades del Sistema Nervioso Autónomo/metabolismo , Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/patología , Sistema Nervioso Entérico/metabolismo , Sistema Nervioso Entérico/patología , Enfermedades de los Caballos/metabolismo , Caballos , Inmunohistoquímica , Masculino , Neuronas/metabolismoRESUMEN
REASONS FOR PERFORMING STUDY: The gastrointestinal pacemaker cells, the interstitial cells of Cajal (ICC), have been implicated in several human gastrointestinal dysmotility syndromes. Recently, the involvement of these cells in equine gastrointestinal diseases has been investigated in cases of equine grass sickness where a significant reduction in ICC density was observed. OBJECTIVE: To investigate ICC density in equine obstructive gastrointestinal disorders using immunohistochemical labelling methods. METHODS: Intestinal samples were analysed from 44 horses undergoing exploratory surgery for colic and from 11 control animals subjected to euthanasia for conditions not related to the gastrointestinal tract. Immunohistochemical labelling of ICC was carried out using an anti-c-Kit antibody. Two independent observers assessed ICC density using a semiquantitative grading system. RESULTS: There was a significant reduction in ICC density in horses with large colon disorders compared to the controls (P<0.01). Horses with strangulating lesions of the small intestine showed no difference when compared to the controls. CONCLUSIONS: There was a reduction in ICC density in horses with large intestinal disorders. POTENTIAL RELEVANCE: The reduction in ICC density may be associated with the clinical findings as well as recurrent colic episodes observed in a number of these cases. This immunohistochemical study provides a basis for future functional electrophysiological investigations to determine the precise effect of ICC reduction on equine intestinal motility.
Asunto(s)
Cólico/veterinaria , Sistema Digestivo/citología , Enfermedades de los Caballos/patología , Obstrucción Intestinal/veterinaria , Proteínas Proto-Oncogénicas c-kit/análisis , Animales , Estudios de Casos y Controles , Cólico/patología , Colon/citología , Colon/patología , Femenino , Caballos , Inmunohistoquímica/veterinaria , Obstrucción Intestinal/patología , Masculino , Proteínas Proto-Oncogénicas c-kit/inmunologíaRESUMEN
This study set out to determine the pattern of development and distribution of the interstitial cells of Cajal (ICC) in the intestinal tract of the equine fetus and neonate. Intestinal tissue samples from 12 naturally aborted equine fetuses and three euthanized neonates were collected and fixed in formalin prior to applying standard immunohistochemical labelling techniques targeting the c-Kit protein of the ICC. At 6 months of gestation, a network of ICC was present in the myenteric plexus region of both the small and the large intestine. ICC were also present within the circular muscle layer. In the large intestine, a proximal to distal gradient of distribution was evident, with few ICC observed in the more distal parts of the large intestine in the younger fetuses compared with the near-term animals. A transmural gradient of distribution was also evident within the large intestine, with the most luminal part of the muscularis externa being the last area to be colonized by ICC. This region did not appear fully developed until the early neonatal period. An increased density of ICC was noted throughout the large intestine in the regions of the taenial bands in all animals. This study is the first to describe ICC development and distribution in the equine fetus and neonate.
Asunto(s)
Caballos/embriología , Intestinos/citología , Animales , Colon/citología , Colon/embriología , Caballos/anatomía & histología , Íleon/citología , Íleon/embriología , Inmunohistoquímica/métodos , Intestino Grueso/citología , Intestino Grueso/embriología , Intestino Delgado/citología , Intestino Delgado/embriología , Intestinos/embriología , Músculo Liso/citología , Músculo Liso/embriología , Plexo Mientérico/citología , Plexo Mientérico/embriología , Proteínas Proto-Oncogénicas c-kit/análisisRESUMEN
Intracellular microelectrode recordings were made from smooth muscle cells in cross-sectional preparations of equine ileum, superfused in vitro. Membrane potential oscillations and spike potentials were recorded in all preparations, but recordings were made more readily from cells in the longitudinal muscle layer than from cells in the circular layer. The mean (se) resting membrane potential (RMP) of smooth muscle cells in the longitudinal muscle layer was -51.9 (1.2) mV, and the membrane potential oscillations in this layer had a mean amplitude of 4.8 (0.4) mV, a frequency of 9.0 (0.1) cycles per minute and a duration of 5.8 (0.2) seconds. The membrane potential oscillations were preserved in the presence of tetrodotoxin. A waxing and waning pattern of membrane potential oscillation activity was observed. Nifedipine abolished the spiking contractile activity of the smooth muscle, did not abolish the membrane potential oscillations but did alter their temporal characteristics.
Asunto(s)
Caballos/fisiología , Íleon/fisiología , Músculo Liso/fisiología , Potenciales de Acción , Animales , Potenciales de la MembranaRESUMEN
The occurrence and density of distribution of nerves and endocrine cells that are immunoreactive for neuropeptides in the bovine pancreas were studied by immunohistochemistry. The six neuropeptides localized were galanin (GAL), substance P (SP), methionine-enkephalin (MENK), neuropeptide Y (NPY), calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP). The exocrine pancreas was shown to have an appreciable number of GAL- and SP-immunoreactive nerve fibres but few fibres showing immunoreactivity for VIP and CGRP. Numerous MENK-, GAL-, SP-, and NPY-immunoreactive nerve fibres were seen in the endocrine portion of the pancreas. Nerve cell bodies in the intrapancreatic ganglia showed immunoreactivity for all of the neuropeptides except CGRP. Endocrine cells showing immunoreactivity for GAL and SP were observed in the large islets and islets of Langerhans, respectively. The present results indicate a characteristic distribution of neuropeptides in the bovine pancreas, which may regulate both exocrine and endocrine secretions of pancreas.
Asunto(s)
Islotes Pancreáticos/citología , Neuropéptidos/análisis , Páncreas/citología , Envejecimiento , Animales , Péptido Relacionado con Gen de Calcitonina/análisis , Bovinos , Encefalina Metionina/análisis , Femenino , Galanina/análisis , Inmunohistoquímica/métodos , Islotes Pancreáticos/crecimiento & desarrollo , Neuropéptido Y/análisis , Páncreas/crecimiento & desarrollo , Sustancia P/análisis , Péptido Intestinal Vasoactivo/análisisRESUMEN
Ileal samples were harvested fresh from euthanized adult horses. The tissues were microdissected to prepare wholemount preparations for immunohistochemistry and for either explant or dissociated culture systems of the enteric nervous system. Explant culture systems were established using whole-mounts of either the submucous plexus or the muscularis externa (including the myenteric plexus). Dissociated cell cultures could only be obtained from the submucous plexus. Culture systems were maintained for up to 5 days. Immunoreactivity for a neuronal marker (Pan-N) and for glial cell markers (GFAP and S100) indicated the presence of both neurons and enteric glia in the tissue culture preparations. This is the first report of equine enteric neurons being grown in tissue culture Further refinements to the techniques will be required before this in vitro model can be used for quantitative analysis.
Asunto(s)
Técnicas de Cultivo/veterinaria , Caballos/anatomía & histología , Íleon/inervación , Plexo Submucoso/fisiología , Animales , Técnicas de Cultivo de Célula/métodos , Técnicas de Cultivo de Célula/veterinaria , Técnicas de Cultivo/métodos , Técnica del Anticuerpo Fluorescente Indirecta , Proteína Ácida Fibrilar de la Glía/química , Caballos/fisiología , Íleon/química , Íleon/fisiología , Microscopía de Contraste de Fase/veterinaria , Proteínas de Neurofilamentos/química , Proteínas S100/química , Plexo Submucoso/química , Plexo Submucoso/citologíaRESUMEN
The interstitial cells of Cajal (ICC) are c-kit immunoreactive cells of the gastrointestinal tract which are suggested to have a role in the control of intestinal motility. Cells with c-kit immunoreactivity have not been previously described in the gastrointestinal tract of the horse. Immunoreactivity for c-kit was revealed using immunohistochemical labelling with an anti-c-kit polyclonal antibody. Sections of normal gastrointestinal tissue were examined from 13 anatomically defined sites from stomach to small colon taken from horses free from gastrointestinal disease. Three types of c-kit immunoreactive cells were identified: spindle-shaped cells in the region of the myenteric plexus, stellate or bipolar cells in the circular muscle layer, and round cells in the submucosa. The round cells were shown to be mast cells with the use of toluidine blue staining, whereas the other c-kit immunoreactive cells did not exhibit metachromasia and were classified as ICC. This study will serve as a basis for future pathological studies in the horse.
Asunto(s)
Sistema Digestivo/citología , Caballos/anatomía & histología , Proteínas Proto-Oncogénicas c-kit/análisis , Animales , Ciego/citología , Colon/citología , Técnica del Anticuerpo Fluorescente/veterinariaRESUMEN
Autonomic dysfunction constitutes a prominent clinical feature of equine grass sickness (EGS). Significant injury to the nervous control of the alimentary system is life threatening, partly because of dysphagia but also because of the failure of the unique regulatory mechanisms in equine digestion involving water and electrolyte balance. The neuropathology also indicates the presence of a somatic polyneuropathy. The morphological features of EGS are similar to those of excitotoxic neuronal degeneration, which resembles neuronal apoptosis. It is difficult to ascertain from published accounts the degree of damage to central neurones: the distribution is well documented and selective but the proportion of damage is poorly quantified. If lesions involve a significant number of regulatory neurones they should produce functional deficits. Any clinical assessment of horses, especially those with chronic EGS, should include a thorough neurological examination. Although this will not necessarily improve the outcome of the case, it may enable the rational selection of animals with a reasonable prognosis for recovery which is partly determined by the extent of CNS lesions. The evidence supports the following pathogenesis. There is an initial lesion in the enteric nervous system of susceptible horses. In the acute form of EGS, massive enteric neuronal damage occurs first functionally, then structurally leading to generalized alimentary smooth muscle atony, enhanced secretions and altered fluid fluxes. Severe distension of the stomach and small intestines rapidly develops, which augments the intestinal ileus by intersegmental inhibitory reflexes and causes colic and dehydration. In subacute cases, failure of intestinal bicarbonate buffer together with alimentary stasis rapidly reduces caecal-colonic fermentation. Thus the osmolality of large intestinal digesta reduces and water travels out of the bowel along osmotic gradients. Water returns to the circulation, but is eventually lost in the gastric and small intestinal secretions. The observation that pathological lesions may not be seen in the prevertebral ganglia within the first few days of acute cases supports the view that a functional deficit precedes structural lesions which may be secondary to a retrograde degeneration. It is therefore possible to resolve the observations that less damage may be seen in prevertebral ganglia and elsewhere in peracute and acute cases with the more common finding that greater neuronal damage is present in acute than in chronic cases. These different observations are probably time dependent. Chronic EGS occurs when there is less initial enteric nerve damage which may lead to less secondary prevertebral ganglionic pathology, and more time for functional and structural compensatory mechanisms to develop. Denervation hypersensitivity develops at target sites both in the gut and in peripheral somatic nerves which may account, in part, for the clinical signs of patchy sweating and muscle tremors. Raised circulating adrenaline levels may also account for generalized sweating, may contribute to gastrointestinal atony and may affect pacemakers at the pelvic flexure. Many of the features of EGS make worthwhile the re-investigation of Clostridium botulinum Group III toxins, which are known to prevent vesicular exocytosis, stimulate neurosecretion, produce neuronal chromatolysis and inhibit neutrophil migration. Also, evidence from other species suggests that increased nitrergic neuronal activity can account for many of the clinical signs of EGS, namely dysphagia, generalized ileus, gastric dilatation, sweating, peripheral vasodilatation, tachycardia, salivary hypersecretion, muscle wastage and cachexia.
Asunto(s)
Enfermedades del Sistema Nervioso Autónomo/veterinaria , Sistema Nervioso Entérico/fisiopatología , Enfermedades de los Caballos/fisiopatología , Caballos/fisiología , Animales , Enfermedades del Sistema Nervioso Autónomo/patología , Enfermedades del Sistema Nervioso Autónomo/fisiopatología , Trastornos de Deglución/fisiopatología , Sistema Digestivo/fisiopatología , Sistema Nervioso Entérico/patología , Enfermedades de los Caballos/patología , Neurotoxinas/toxicidad , Neurotransmisores/fisiologíaRESUMEN
Intracellular recordings were made from neurones in the internal submucosal plexus (ISP) of porcine small intestine and synaptic inputs were investigated by focal stimulation of nerve fiber tracts. Nicotinic fast excitatory potentials (e.p.s.p.s) were recorded in all neurones, but slow e.p.s.p.s and slow inhibitory potentials (i.p.s.p.s) were rarely seen. Membrane potential changes similar to those occurring during the slow e.p.s.p. and slow i.p.s.p. could be evoked by exogenous application of neurotransmitters, even in neurones failing to display a nerve-mediated response. We suggest that the predominant source of the slow synaptic inputs to the ISP may be the neurones of the external submucosal plexus (ESP). The failure to record slow e.p.s.p.s and i.p.s.p.s could be a consequence of the anatomical arrangement of the submucosal plexuses whereby interconnecting strands between the ISP and ESP are inaccessible to the focal stimulation.
Asunto(s)
Yeyuno/inervación , Neuronas/fisiología , Neurotransmisores/farmacología , Plexo Submucoso/fisiología , Porcinos/fisiología , Transmisión Sináptica/fisiología , Animales , Animales Recién Nacidos , Potenciales Postsinápticos Excitadores/fisiología , Femenino , Neuronas/efectos de los fármacos , Plexo Submucoso/citología , Plexo Submucoso/efectos de los fármacos , Porcinos/anatomía & histología , Transmisión Sináptica/efectos de los fármacosRESUMEN
Intracellular recordings were made from the internal and external submucosal ganglia of the porcine small intestine and neuronal properties were classified using two existing schemes for guinea-pig enteric neurones. In the first analysis, 77% of cells were designated as Type 4 since they were a heterogeneous population of neurones with the overlapping properties of S/Type 1 and AH/Type 2. The simplicity and usefulness of the second classification scheme was due to its emphasis on a single electrophysiological event, namely, the long-lasting after-hyperpolarization (AH) following the action potential. Eighty-eight percent of the cells studied were thus categorized as either AH (with an AH) or S (without an AH). All S neurones displayed fast synaptic potentials in response to stimulation of interganglionic fibre strands. AH neurones were subdivided into two groups dependent on whether they received fast synaptic inputs. Only by employing the second scheme of classification were differences in the neuronal characteristics and synaptic profiles between the two submucosal plexuses detected. It is concluded that the S and AH system of classification is the most appropriate method for the analysis of intracellular recordings from submucosal neurones in the porcine small intestine.
Asunto(s)
Yeyuno/inervación , Neuronas/fisiología , Plexo Submucoso/fisiología , Porcinos/fisiología , Animales , Animales Recién Nacidos , Femenino , Potenciales de la Membrana/fisiología , Neuronas/clasificación , Plexo Submucoso/citología , Porcinos/anatomía & histologíaRESUMEN
Light microscopy was undertaken on sections from the caudal flexure of the duodenum and the terminal ileum proximal to the ileocaecal fold in 5 control horses, 5 horses with acute grass sickness (AGS), and 5 horses with chronic grass sickness (CGS). With the exception of the ileal submucous plexus of the CGS group, the AGS group had the lowest number of neurons as measured using a subjective scoring scheme. The proportion of abnormal neurons in the AGS group was similar in both plexuses and both regions, whereas the values for the CGS group were much higher in the duodenal region than in the ileal region. The motility of tissue adjacent to that used for histology was measured isometrically in vitro. The increase in the rate of contractions following exposure to physostigmine was greatest for the AGS group, both from the duodenal and from the ileal region. The latency was longest for the AGS group, suggesting that the material from this group had the least number of active cholinergic neurons. The studies with physostigmine thus indicated that the most severe functional damage occurred in cases of AGS. These findings confirm that extensive damage occurs in the enteric neurons in equine grass sickness. There was good correlation between the functional cholinergic responses and the extent of neuronal degeneration.
Asunto(s)
Enfermedades del Sistema Nervioso Autónomo/veterinaria , Sistema Nervioso Autónomo/patología , Duodeno/inervación , Enfermedades de los Caballos/patología , Íleon/inervación , Neuronas Motoras/efectos de los fármacos , Parasimpaticomiméticos/farmacología , Fisostigmina/farmacología , Enfermedad Aguda , Animales , Sistema Nervioso Autónomo/efectos de los fármacos , Sistema Nervioso Autónomo/fisiopatología , Enfermedades del Sistema Nervioso Autónomo/patología , Enfermedad Crónica , Duodeno/patología , Femenino , Caballos , Íleon/patología , Masculino , Neuronas Motoras/patología , Neuronas Motoras/fisiologíaRESUMEN
1. Intracellular microelectrodes were used to identify three major electrophysiological categories of neurone in both the internal and external submucous plexuses of the porcine small intestine. 2. Two classes of neurone with a long-lasting after-hyperpolarization following their action potential were differentiated by the presence or absence of fast excitatory synaptic inputs (EPSPs) and were termed AH neurones. S neurones received fast EPSPs but did not display after-hyperpolarizations. 3. The mean resting membrane potentials of the three groups of neurones showed a similar trend in both plexuses, with significantly higher values for the two populations of AH neurone than for S neurones. No significant variation of input resistance with cell type was detected. Neuronal input resistance was significantly greater in the internal submucous plexus than in the external submucous plexus. 4. Over 80% of AH neurones in the internal submucous plexus displayed fast EPSPs but a similar percentage of AH neurones in the external submucous plexus did not show fast EPSPs. S neurones constituted 60% of cells studied in the internal submucous plexus but less than 30% of the cell population in the external submucous plexus. 5. This study of porcine submucous neurones has revealed both similarities and differences to previous work in the guinea-pig small intestine. The most contrasting features are the relative abundance and subclassification of AH neurones in the pig in addition to the apparent paucity of slow synaptic potentials. The differences in the neuronal profiles of the internal and external submucous plexuses may reflect a differentiation of function between the two enteric nerve networks.
Asunto(s)
Animales Recién Nacidos/fisiología , Intestino Delgado/inervación , Neuronas/fisiología , Plexo Submucoso/fisiología , Animales , Electrofisiología , Femenino , Ganglios Simpáticos/citología , Ganglios Simpáticos/fisiología , Intestino Delgado/fisiología , Potenciales de la Membrana/fisiología , Microelectrodos , PorcinosRESUMEN
The submucous plexus of large mammals like dog, horse, cow, sheep, pig and man consists of more than one easily identified plexus. The divisions of the submucous plexus are known as the external submucous plexus and the internal submucous plexus. Recently findings have shown that there exists functional differences between the neuronal populations in the subdivisions of the submucous plexus in the small intestine of pigs. We report here how to obtain whole mounts of the submucous plexus containing both the internal and the external submucous plexus. The whole mounts from the submucous plexus of the pig contains almost no muscle and can be used in intracellular neuronal studies without adding nifedipine or equivalent L-type Ca2+ channel blockers to inhibit the contractions of the smooth muscle.
Asunto(s)
Ganglios/citología , Intestino Delgado/inervación , Porcinos/anatomía & histología , Animales , Disección , Femenino , Mucosa Intestinal/inervaciónRESUMEN
Small intestine was taken from the caudal flexure of the duodenum and the terminal ileum proximal to the ileocaecal fold of 25 horses, 9 with acute grass sickness (AGS), 12 with subacute grass sickness (SAGS) and 12 with chronic grass sickness (CGS). The motility in the samples was measured isometrically either within 1 h of death or after storage for 24 h at 4 degree C. In control tissue, noradrenaline produced contractions of muscle strips which did not involve a muscarinic cholinergic mechanism and which were unaffected by the alpha 1 antagonist prazosin but were blocked by the alpha 2 antagonist yohimbine. Pretreatment with the alpha antagonist phentolamine prevented the contractile response to noradrenaline and the background contractions either continued at a reduced rate and amplitude or were abolished after a few minutes. Thus, following alpha blockade, noradrenaline reduced the background contraction rate by an effect on inhibitory beta adrenoceptors. The rate of background contractions in duodenal preparations was significantly greater than that in control ideal preparations. Although cold storage for 24 h caused a reduction in the background contraction rates of the control preparations, there was no effect on the contractile responses to noradrenaline, the associated pharmacology being similar to that of fresh tissue. This suggests that noradrenaline-evoked contraction was not dependent on enteric neural elements. The response to noradrenaline by grass sickness-affected tissue was generally similar to that of tissue from control horses, with an immediate contraction which was alpha 2 sensitive. The contractile response to noradrenaline after propranolol was significantly reduced in the CGS group and there were significant differences between the AGS, CGS and control groups. There was a significant difference between the ileal preparations from the control and SAGS groups in their response to noradrenaline following pretreatment with propranolol.
Asunto(s)
Agonistas alfa-Adrenérgicos/farmacología , Enfermedades del Sistema Nervioso Autónomo/veterinaria , Enfermedades de los Caballos/fisiopatología , Intestino Delgado/efectos de los fármacos , Norepinefrina/farmacología , Antagonistas Adrenérgicos alfa/farmacología , Animales , Enfermedades del Sistema Nervioso Autónomo/fisiopatología , Relación Dosis-Respuesta a Droga , Duodeno/efectos de los fármacos , Duodeno/fisiología , Epinefrina/farmacología , Femenino , Caballos , Íleon/efectos de los fármacos , Íleon/fisiología , Técnicas In Vitro , Intestino Delgado/fisiología , Masculino , Contracción Muscular/efectos de los fármacos , Contracción Muscular/fisiología , Músculo Liso/efectos de los fármacos , Músculo Liso/fisiología , Fentolamina/farmacología , Prazosina/farmacología , Factores de Tiempo , Yohimbina/farmacologíaRESUMEN
A special configuration of the data acquisition software package Spike2 (CED) has been developed to allow interactive computer control of a current-clamp intracellular recording system. Using the 1401plus dedicated computer (CED) as an interface between the electrophysiological apparatus and a personal computer it was possible to have keyboard-control of intracellular current injection, single and repetitive pulse nerve stimulation, pressure ejection as well as on-going data acquisition. An analysis program was designed using the Spike2 programming language for the investigation of resting membrane properties, spike characteristics and synaptic input profiles of enteric neurones. The hardware configurations and associated software of our set-up may be of interest to electrophysiologists wishing to implement or extend a computer-based experimental system.