Proliferative enteropathy (PE)-induced changes in the calbindin-immunoreactive (CB-IR) neurons of inferior mesenteric ganglion supplying the descending colon in the pig

Changes in the Population Size of Calbindin D-28k-Immunoreactive Enteric Neurons in the Porcine Caecum under the Influence of Bisphenol A: A Preliminary Study

Calbindin D-28k (CB) is a calcium-binding protein widely distributed in living organisms that may act as a calcium buffer and sensory protein. CB is present in the enteric nervous system (ENS) situated in the gastrointestinal tract, which controls the majority of activities of the stomach and intestine. The influence of various doses of bisphenol A (BPA)—a chemical compound widely used in plastics production—on the number and distribution of CB-positive enteric neuronal cells in the porcine caecum was investigated with an immunofluorescence technique. The obtained results showed that low dosages of BPA resulted in an increase in the number of CB-positive neuronal cells in the myenteric (MP) and inner submucous (ISP) plexuses, whereas it did not alter the number of such neuronal cells in the outer submucous plexus (OSP). High dosages of BPA caused the increase in the amount of CB-positive perikarya in all the above-mentioned kinds of the caecal neuronal plexuses. These observations strongly suggest that CB in the ENS participates in the processes connected with the toxic activity of BPA. Most likely, the changes noted in this experiment result from the adaptive and protective properties of CB.

Somatostatin as an Active Substance in the Mammalian Enteric Nervous System

Somatostatin (SOM) is an active substance which most commonly occurs in endocrine cells, as well as in the central and peripheral nervous system. One of the parts of the nervous system where the presence of SOM has been confirmed is the enteric nervous system (ENS), located in the wall of the gastrointestinal (GI) tract. It regulates most of the functions of the stomach and intestine and it is characterized by complex organization and a high degree of independence from the central nervous system. SOM has been described in the ENS of numerous mammal species and its main functions in the GI tract are connected with the inhibition of the intestinal motility and secretory activity. Moreover, SOM participates in sensory and pain stimuli conduction, modulation of the release of other neuronal factors, and regulation of blood flow in the intestinal vessels. This peptide is also involved in the pathological processes in the GI tract and is known as an anti-inflammatory agent. This paper, which focuses primarily on the distribution of SOM in the ENS and extrinsic intestinal innervation in various mammalian species, is a review of studies concerning this issue published from 1973 to the present.

Neurochemical characterization of intramural nerve fibres in the porcine oesophagus

The gastrointestinal (GI) tract is innervated by nerve processes derived from the intramural enteric neurons and neurons localized outside the digestive tract. This study analysed the neurochemical characterization of nerves in the wall of the porcine oesophagus using single immunofluorescence technique. Immunoreactivity to vesicular acetylcholine transporter (VAChT), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), somatostatin (SOM), galanin (GAL), neuronal isoform of nitric oxide synthase (nNOS), substance P (SP), leucine enkephalin (LENK), calcitonin gene-related peptide (CGRP) or dopamine beta-hydroxylase (DBH) was investigated in intramuscular and intramucosal nerves of the cervical, thoracic and abdominal oesophagus. The results indicate that all of the substances studied were present in the oesophageal nerves. The density of particular populations of fibres depended on the segment of the oesophagus. The most numerous were fibres immunoreactive to VIP in the longitudinal and circular muscle layers of the abdominal oesophagus: The number of these fibres amounted to 16.4 ± 0.8 and 18.1 ± 3.1, respectively. In turn, the least numerous were CGRP-positive fibres, which were present only in the circular muscle layer of the cervical oesophagus and mucosal layer of the abdominal oesophagus in the number of 0.3 ± 0. The obtained results show that nerves in the porcine oesophageal wall are very diverse in their neurochemical coding, and differences between particular parts of the oesophagus suggest that organization of the innervation clearly depends on the fragment of this organ.

The influence of experimental inflammation and axotomy on leucine enkephalin (leuENK) distribution in intramural nervous structures of the porcine descending colon

Background

The enteric nervous system (ENS), located in the intestinal wall and characterized by considerable independence from the central nervous system, consists of millions of cells. Enteric neurons control the majority of functions of the gastrointestinal tract using a wide range of substances, which are neuromediators and/or neuromodulators. One of them is leucine–enkephalin (leuENK), which belongs to the endogenous opioid family. It is known that opioids in the gastrointestinal tract have various functions, including visceral pain conduction, intestinal motility and secretion and immune processes, but many aspects of distribution and function of leuENK in the ENS, especially during pathological states, remain unknown.

Results

During this experiment, the distribution of leuENK – like immunoreactive (leuENK-LI) nervous structures using the immunofluorescence technique were studied in the porcine colon in physiological conditions, during chemically-induced inflammation and after axotomy. The study included the circular muscle layer, myenteric (MP), outer submucous (OSP) and inner submucous plexus (ISP) and the mucosal layer. In control animals, the number of leuENK-LI neurons amounted to 4.86 ± 0.17%, 2.86 ± 0.28% and 1.07 ± 0.08% in the MP, OSP and ISP, respectively. Generally, both pathological stimuli caused an increase in the number of detected leuENK-LI cells, but the intensity of the observed changes depended on the factor studied and part of the ENS. The percentage of leuENK-LI perikarya amounted to 11.48 ± 0.96%, 8.71 ± 0.13% and 9.40 ± 0.76% during colitis, and 6.90 ± 0.52% 8.46 ± 12% and 4.48 ± 0.44% after axotomy in MP, OSP and ISP, respectively. Both processes also resulted in an increase in the number of leuENK-LI nerves in the circular muscle layer, whereas changes were less visible in the mucosa during inflammation and axotomy did not change the number of leuENK-LI mucosal fibers.

Conclusions

LeuENK in the ENS takes part in intestinal regulatory processes not only in physiological conditions, but also under pathological factors. The observed changes are probably connected with the participation of leuENK in sensory and motor innervation and the neuroprotective effects of this substance. Differences in the number of leuENK-LI neurons during inflammation and after axotomy may suggest that the exact functions of leuENK probably depend on the type of pathological factor acting on the intestine.

Weaning stress and gastrointestinal barrier development: Implications for lifelong gut health in pigs

The gastrointestinal (GI) barrier serves a critical role in survival and overall health of animals and humans. Several layers of barrier defense mechanisms are provided by the epithelial, immune and enteric nervous systems. Together they act in concert to control normal gut functions (e.g., digestion, absorption, secretion, immunity, etc.) whereas at the same time provide a barrier from the hostile conditions in the luminal environment. Breakdown of these critical GI functions is a central pathophysiological mechanism in the most serious GI disorders in pigs. This review will focus on the development and functional properties of the GI barrier in pigs and how common early life production stressors, such as weaning, can alter immediate and long-term barrier function and disease susceptibility. Specific stress-related pathophysiological mechanisms responsible for driving GI barrier dysfunction induced by weaning and the implications to animal health and performance will be discussed.

Distribution and immunohistochemical characteristics of cocaine- and amphetamineregulated transcript-positive nerve elements in the pelvic ganglia of the female pig

Cocaine- and amphetamine-regulated transcript (CART) peptides are widely expressed not only in the brain but also in numerous endocrine/neuroendocrine cells as well as in neurons of the peripheral nervous system. The present study investigated the distribution patterns of CART-like immunoreactivity in the pelvic plexus (PP) of the female pig. The co-expression of CART with principal neurotransmitter markers: choline acetyltransferase (ChAT), tyrosine hydroxylase (TH), serotonin (5-HT) or biologically active neuropeptides: pituitary adenylate cyclase-activating polypeptide (PACAP), substance P (SP), calbindin was analyzed using double immunohistochemical stainings. Amongst neurons immunopositive to Hu C/D panneuronal marker as many as 4.1 ± 1.2% in right and 4.4 ± 1.6% in left pelvic ganglia were found to express CART. The vast majority of CART-IR ganglionic neurons were predominantly small in size and were evenly scattered throughout particular ganglia. Immunoreactivity to CART was also detected in numerous nerve terminals (which frequently formed pericellular formations around CART-negative perikarya) as well as in numerous nerve fibres within nerve branches interconnecting the unilateral pelvic ganglia. Immunohistochemistry revealed that virtually all CART-IR neurons were cholinergic in nature and CART-IR basket-like formations frequently encircled TH-positive/CART-negative perikarya. None of CART-IR ganglionic neurons showed immunoreactivity to SP, PACAP, 5-HT or calbindin. CART-IR nerve fibres ran in a close vicinity to serotonin-containing cells or faintly labelled SP-expressing neurons. On the other hand, PACAP-IR, SP-IR (but not 5-HT-positive) nerve terminals were found to run in close proximity to CART-IR neurons. Our results indicate that: 1) CART present in PP may influence the activity of pelvic ganglionic neurons/SIF cells, 2) PP should be considered as a potential source of CART-like supply to pelvic viscera and 3) functional interactions between CART and SP or PACAP are possible at the periphery.

The Influence of Low Doses of Zearalenone and T-2 Toxin on Calcitonin Gene Related Peptide-Like Immunoreactive (CGRP-LI) Neurons in the ENS of the Porcine Descending Colon

The enteric nervous system (ENS) can undergo adaptive and reparative changes in response to physiological and pathological stimuli. These manifest primarily as alterations in the levels of active substances expressed by the enteric neuron. While it is known that mycotoxins can affect the function of the central and peripheral nervous systems, knowledge about their influence on the ENS is limited. Therefore, the aim of the present study was to investigate the influence of low doses of zearalenone (ZEN) and T-2 toxin on calcitonin gene related peptide-like immunoreactive (CGRP-LI) neurons in the ENS of the porcine descending colon using a double immunofluorescence technique. Both mycotoxins led to an increase in the percentage of CGRP-LI neurons in all types of enteric plexuses and changed the degree of co-localization of CGRP with other neuronal active substances, such as substance P, galanin, nitric oxide synthase, and cocaine- and amphetamine-regulated transcript peptide. The obtained results demonstrate that even low doses of ZEN and T-2 can affect living organisms and cause changes in the neurochemical profile of enteric neurons.

Acetylsalicylic acid-induced changes in the chemical coding of extrinsic sensory neurons supplying the prepyloric area of the porcine stomach

Acetylsalicylic acid is a popular drug that is commonly used to treat fever and inflammation, but which can also negativity affect the mucosal layer of the stomach, although knowledge concerning its influence on gastric innervation is very scarce. Thus, the aim of the present study was to study the influence of prolonged acetylsalicylic acid supplementation on the extrinsic primary sensory neurons supplying the porcine stomach prepyloric region. Fast Blue (FB) was injected into the above-mentioned region of the stomach. Acetylsalicylic acid was then given orally to the experimental gilts from the seventh day after FB injection to the 27th day of the experiment. After euthanasia, the nodose ganglia (NG) and dorsal root ganglia (DRG) were collected. Sections of these ganglia were processed for routine double-labelling immunofluorescence technique for substance P (SP), calcitonine gene related peptide (CGRP), galanin (GAL), neuronal isoform of nitric oxide synthase (nNOS) and vasoactive intestinal polypeptide (VIP). Under physiological conditions within the nodose ganglia, the percentage of the FB-labeled neurons immunoreactive to particular substances ranged between 17.9 ± 2.7% (VIP-like immunoreactive (LI) neurons in the right NG) and 60.4 ± 1.7% (SP-LI cells within the left NG). Acetylsalicylic acid supplementation caused a considerable increase in the expression of all active substances studied within both left and right NG and the percentage of neurons positive to particular substances fluctuated from 47.2 ± 3.6% (GAL-LI neurons in the right NG) to 67.2 ± 2.0% (cells immunoreactive to SP in the left NG). All studied substances were also observed in DRG neurons supplying the prepyloric region of the stomach, but the number of immunoreactive neurons was too small to conduct a statistical analysis. The obtained results show that ASA may influence chemical coding of the sensory neurons supplying the porcine stomach, but the exact mechanisms of this action still remain unknown.

Neurochemical Plasticity of the Coeliac-Superior Mesenteric Ganglion Complex Neurons Projecting to the Prepyloric Area of the Porcine Stomach following Hyperacidity

This study was designed to determine neurochemical properties of the coeliac-superior mesenteric ganglion (CSMG) neurons supplying the prepyloric area of the porcine stomach in physiological state and following experimentally induced hyperacidity. To localize sympathetic neurons innervating the studied area of stomach, the neuronal retrograde tracer Fast Blue (FB) was applied to control animals and hydrochloric acid infusion (HCl) groups. After 23 days, animals of the HCl group were reintroduced into a state of general anesthesia and intragastrically given 5 mL/kg of body weight of 0.25 M aqueous solution of hydrochloric acid. On the 28th day, all animals were sacrificed. The CSMG complexes were then collected and processed for double-labeling immunofluorescence. In the control animals, FB-positive perikarya displayed immunoreactivity to tyrosine hydroxylase (TH), dopamine β-hydroxylase (DβH), neuropeptide Y (NPY), and galanin (GAL). Experimentally induced gastric hyperacidity changed the neurochemical phenotype of the studied neurons. An upregulated expression of GAL and NPY and the de novo synthesis of neuronal nitric oxide synthase (nNOS) and leu5-enkephalin (LENK) as well as downregulated expression of TH and DβH in the stomach-projecting neurons were observed. These findings enrich existing knowledge about the participation of these active substances in adaptive mechanism(s) of the sympathetic neurons during pathological processes within the gastrointestinal tract.

The Influence of Prolonged Acetylsalicylic Acid Supplementation-Induced Gastritis on the Neurochemistry of the Sympathetic Neurons Supplying Prepyloric Region of the Porcine Stomach

This experiment was designed to establish the localization and neurochemical phenotyping of sympathetic neurons supplying prepyloric area of the porcine stomach in a physiological state and during acetylsalicylic acid (ASA) induced gastritis. In order to localize the sympathetic perikarya the stomachs of both control and acetylsalicylic acid treated (ASA group) animals were injected with neuronal retrograde tracer Fast Blue (FB). Seven days post FB injection, animals were divided into a control and ASA supplementation group. The ASA group was given 100 mg/kg of b.w. ASA orally for 21 days. On the 28^th day all pigs were euthanized with gradual overdose of anesthetic. Then fourteen-micrometer-thick cryostat sections were processed for routine double-labeling immunofluorescence, using primary antisera directed towards tyrosine hydroxylase (TH), dopamine β-hydroxylase (DβH), neuropeptide Y (NPY), galanin (GAL), neuronal nitric oxide synthase (nNOS), leu 5-enkephalin (LENK), cocaine- and amphetamine- regulated transcript peptide (CART), calcitonin gene-related peptide (CGRP), substance P (SP) and vasoactive intestinal peptide (VIP). The data obtained in this study indicate that postganglionic sympathetic nerve fibers supplying prepyloric area of the porcine stomach originate from the coeliac-cranial mesenteric ganglion complex (CCMG). In control animals, the FB-labelled neurons expressed TH (94.85 ± 1.01%), DβH (97.10 ± 0.97%), NPY (46.88 ± 2.53%) and GAL (8.40 ± 0.53%). In ASA group, TH- and DβH- positive nerve cells were reduced (85.78 ± 2.65% and 88.82 ± 1.63% respectively). Moreover, ASA- induced gastritis resulted in increased expression of NPY (76.59 ± 3.02%) and GAL (26.45 ± 2.75%) as well as the novo-synthesis of nNOS (6.13 ± 1.11%) and LENK (4.77 ± 0.42%) in traced CCMG neurons. Additionally, a network of CART-, CGRP-, SP-, VIP-, LENK-, nNOS- immunoreactive (IR) nerve fibers encircling the FB-positive perikarya were observed in both intact and ASA-treated animals. The results of this study indicate involvement of these neuropeptides in the development or presumably counteraction of gastric inflammation.

Architecture and Chemical Coding of the Inner and Outer Submucous Plexus in the Colon of Piglets

In the porcine colon, the submucous plexus is divided into an inner submucous plexus (ISP) on the epithelial side and an outer submucous plexus (OSP) on the circular muscle side. Although both plexuses are probably involved in the regulation of epithelial functions, they might differ in function and neurochemical coding according to their localization. Therefore, we examined expression and co-localization of different neurotransmitters and neuronal markers in both plexuses as well as in neuronal fibres. Immunohistochemical staining was performed on wholemount preparations of ISP and OSP and on cryostat sections. Antibodies against choline acetyltransferase (ChAT), substance P (SP), somatostatin (SOM), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), neuronal nitric oxide synthase (nNOS) and the pan-neuronal markers Hu C/D and neuron specific enolase (NSE) were used. The ISP contained 1,380 ± 131 ganglia per cm² and 122 ± 12 neurons per ganglion. In contrast, the OSP showed a wider meshwork (215 ± 33 ganglia per cm²) and smaller ganglia (57 ± 3 neurons per ganglion). In the ISP, 42% of all neurons expressed ChAT. About 66% of ChAT-positive neurons co-localized SP. A small number of ISP neurons expressed SOM. Chemical coding in the OSP was more complex. Besides the ChAT/±SP subpopulation (32% of all neurons), a nNOS-immunoreactive population (31%) was detected. Most nitrergic neurons were only immunoreactive for nNOS; 10% co-localized with VIP. A small subpopulation of OSP neurons was immunoreactive for ChAT/nNOS/±VIP. All types of neurotransmitters found in the ISP or OSP were also detected in neuronal fibres within the mucosa. We suppose that the cholinergic population in the ISP is involved in the control of epithelial functions. Regarding neurochemical coding, the OSP shares some similarities with the myenteric plexus. Because of its location and neurochemical characteristics, the OSP may be involved in controlling both the mucosa and circular muscle.

Origins and neurochemical complexity of preganglionic neurons supplying the superior cervical ganglion in the domestic pig

The superior cervical ganglion (SCG) is a center of sympathetic innervation of all head and neck organs. SCG sympathetic preganglionic neurons (SPN) were found in the nucleus intermediolateralis pars principalis (IMLpp), the nucleus intermediolateralis pars funicularis (IMLpf), the nucleus intercalatus spinalis (IC), and the nucleus intercalatus spinalis pars paraependymalis (ICpe). Despite its importance, little is known of SCG innervation and chemical coding in the laboratory pig, a model that is physiologically and anatomically representative of humans. Here in our study, we established the distribution and chemical coding of Fast Blue (FB) retrogradely labelled SPN innervating porcine SCG. After unilateral injection of FB retrograde tracer into the left SCG, labeled neurons were found solely on the ipsilateral side with approximately 98 % located in Th₁–Th₃ segments and predominantly distributed in the IMLpp and IMLpf. Neurochemical analysis revealed that approximately 80 % of SPN were positive both to choline acetyltransferase (ChAT) and nitric oxide synthase (NOS) and were surrounded by a plethora of opioidergic and peptiergic nerve terminals. The results of our study provide a detailed description of the porcine preganglionic neuroarchitecture of neurons controlling the SCG, setting the stage for further studies concerning SPN plasticity under experimental/pathological conditions.

Endogenous opiates and behavior: 2012

This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Substance P as a neuronal factor in the enteric nervous system of the porcine descending colon in physiological conditions and during selected pathogenic processes

The present investigation pertains to changes in substance P-like immunoreactive (SP-LI) nerve structures of the enteric nervous system (ENS) in the porcine descending colon, caused by chemically-induced inflammation and nerve injury (axotomy). The distribution pattern of SP-LI structures was studied using the double immunofluorescence technique in the myenteric (MP), outer submucous (OSP) and inner submucous (ISP) plexuses, as well as in the circular muscle and mucosal layers. Under physiological conditions, SP-LI neurons have been shown to constitute 4.13 ± 0.24%, 3.36 ± 0.26%, and 7.92 ± 0.16% in the MP, OSP, and ISP, respectively. Changes in SP-immunoreactivity depended on the pathological factor studied. The numbers of the SP-LI perikarya amounted to 7.89 ± 0.34, 5.56 ± 0.30, and 19.96 ± 0.57 in chemically-induced colitis, and 4.28 ± 0.13%, 7.18 ± 20%, and 11.62 ± 0.48% after axotomy in MP, OSP, and ISP, respectively. The both studied processes generally resulted in an increase in the number of SP-LI nerve fibers in the circular muscle and mucosal layers. The obtained results suggest that SP-LI nerve structures of the ENS may participate in various pathological processes in the porcine descending colon and exact functions of SP probably depend on the type of the pathological factor.