The enteric nervous system (ENS) runs within the intestinal wall and is responsible for initiating and enacting several reflexes and motor patterns, including peristalsis and the complex interdigestive motor programs, known as migrating motor complexes (MMCs). The ENS consists of several neuron types including intrinsic sensory neurons, interneurons and motor neurons. A great deal is known about the anatomy, pharmacology and electrophysiology of the ENS, yet there is almost no understanding of how enteric neural circuits perform the functions that they do and how they switch from one function to another. The ENS contains intrinsic sensory neurons (ISNs) that connect to every neuron type in the ENS, including making recurrent connections amongst themselves. Thus, they are likely to play a key role, not just in sensory transduction, but in coordination of reflexes and motor patterns. This thesis has explored how these functions are performed by developing and analysing mathematical and computer models of the network of ISNs. (For complete abstract open document)

Associations between the use of antibiotics and altered brain function and mental illness are now well evidenced from animal models and clinical trials. Based on these findings, emerging research efforts have largely focused on how high-dose antibiotic- mediated perturbations of the gut microbiota result in altered neurophysiological and behavioural outcomes. However, these studies have not investigated whether antibiotics also act directly on the host nervous system. My central hypothesis is that high-dose antibiotics, as used in experimental models testing the modulatory role of the gut microbiome, can induce pathophysiological outcomes by direct interaction with enteric neuronal circuits. I designed two sets of experiments to characterize the acute effect of high-dose antibiotics on gut motility and gut-brain neuronal signalling. The first experimental study aimed to determine whether acute exposure of the gastrointestinal tract to high-dose antibiotics directly modulates enteric neurons, with consequences for gut motility. To test this, I used enteric nervous system dependent motility reflexes, ex vivo, as an index of putative effects on the intestinal nervous system. The results of these experiments have shown that luminal antibiotics alter oral to anal propulsive peristalsis in a system where such motility is dependent on the enteric nervous system. The second study aimed to test whether these local effects modulate brain function and behaviour by altering responses of vagal afferent pathways. I performed single-unit recordings from the mesenteric nerve bundle in ex vivo preparations to test this research question. The results suggest that antibiotics can increase activity of extrinsic vagal afferent neurons largely through cholinergic synapses with myenteric IPANs. The present work offers significant therapeutic implications, although its main relevance is in the interpretation of the experimental use of high-dose antibiotics on animal models and where effects on behaviour and the nervous system are attributed solely to alterations in the microbiome. / Thesis / Master of Science (MSc) / Little is known about the mechanisms by which high-dose antibiotics produce changes in gut-brain signalling to negatively affect brain functions and behaviour. Although the general consensus is that these changes are caused by antibiotic-mediated perturbations of the gut microbiota, whether high-dose antibiotics also act directly on the nervous system remains a topic of debate. I have hypothesized that high-dose antibiotics, as used in experimental models associating pathophysiological outcomes to gut microbial changes, also produce adverse effects by direct modulation of enteric neuronal circuits. Indeed, our findings suggest that high-dose antibiotics directly signal to enteric neurons, which locally regulate gut motility reflexes and can transmit that information further to vagal neurons, to influence homeostatic regulation of brain functions and behaviour. This work offers novel therapeutic potential for antibiotics and advises careful interpretation of studies that have attributed effects of high-dose antibiotics solely to alterations in the gut microbiome.

No / The neuromedin U (NMU) receptors, NMU1 and NMU2, are expressed in the gut but their functions are unclear. This study explores the role of NMU in gastrointestinal motility. Experimental approach: The effects of NMU were examined in the forestomach and colon isolated from NMU2R wild-type and NMU2R-/- (knockout) mice, looking for changes in muscle tension and in nerve-mediated responses evoked by electrical field stimulation (EFS), and in models of peristalsis in mouse colon and faecal pellet transit in guinea-pig colon. Key results: In the mouse forestomach, NMU (1 nM-10 ¿M) concentration-dependently induced muscle contraction, in the presence of tetrodotoxin and atropine, in preparations from both wild-type and NMU2R-/- mice (pEC50: 7.9, 7.6, Emax: 0.26, 0.20g tension, respectively, n=8 each concentration). The same concentrations of NMU had no consistent effects on the responses to EFS (n=8). In the mouse colon, NMU (0.1 nM-1 ¿M) had no significant effect on baseline muscle tension (n=8), but concentration-dependently potentiated EFS-evoked contractions in preparations from both wild-type and NMU2R-/- mice, pEC50: 8.1, 7.8, Emax: 24%, 21%, respectively, n=6-11. NMU (0.01 nM-0.1 ¿M, n=5-7) concentration-dependently decreased the interval between waves of peristalsis in the mouse colon (pEC50: 8.8) and increased the rate at which a faecal pellet moved along the guinea-pig colon. Conclusions and implications: These results demonstrate that NMU exerts colon-specific, nerve-mediated, prokinetic activity, via a pathway involving activation of NMU1 receptors. This suggests that this receptor may represent a molecular target for the treatment of intestinal motility disorders.

Embora diversos trabalhos relatem as alterações fisiológicas que ocorrem no trato gastrointestinal com a senescência e com o exercício físico, poucos são os relatos morfológicos a respeito destas duas variantes. Portanto, o objetivo deste trabalho foi verificar qual a influência da atividade física (corrida em esteira) na ultraestrutura, na densidade neuronal (neurônios/mm2) e na área do perfil do corpo celular (µm2) dos neurônios mioentéricos do jejuno de ratos com a idade. Para tanto, foram utilizados 45 ratos Wistar divididos em três grupos: C (controle com seis meses), S (sedentário com 12 meses) e T (treinado com 12 meses) sendo utilizado 5 animais para cada técnica/grupo. Os preparados de membrana do jejuno foram corados com as técnicas histoquímicas de NADH e NADPH para estimar o número de neurônios e a área do perfil neuronal. Os resultados alcançados nos testes de esforço (TEMs) forçam sempre maiores no grupo T do que no grupo S. O peso dos animais do grupo T foi menor que os do grupo S. A área do jejuno-íleo foi mensurada e não presentou diferença significativa (P>0,05) entre os animais dos grupos C, S e T. Com exceção da membrana basal que apresentou-se menos definida e da região periganglionar que encontrava-se mais espassada nos animais do grupo S, não foram identificadas alterações ultraestruturais e no arranjo do plexo mioentéricos entre os grupos. A densidade dos neurônios reativos a NADH-diaforase foi menor (P<0,05) nos animais do grupo S (67,76±3,7) em relação aos animais dos grupos C (104,8±5,86) e T (95,18±7,18). Para os neurônios NADPH-diaforase, observou-se menor densidade neuronal nos grupos S (32,32±1,7) e T (27,39±1,2) comparado com o grupo C (44,53±4,5), mas diferenças significativas não foram evidencias entre os grupos S e T. A área do perfil do corpo celular (µm2) dos neurônios NADH- diaforase positivos diminuiu no grupo S (103,4±8,68) e aumento no grupo T (198,4±8,22) em relação ao grupo C (167±6,93). A área neuronal mensurada nos neurônios NADPH-diaforase positivos foi estatisticamente menor entre os grupos T (129,9±9,55) e C (186,8±9,34), mas não foram observadas diferenças entre estes grupos com o grupo S (157,3±3,64). Contudo, as alterações observadas indicam poucas são as influências do envelhecimento em animais com 12 meses de idade. / Although several works tell the physiologic alterations that they happen in the treatment gastrointestinal with the aging and with the physical exercise, few are the morphologic reports regarding these two variants. Therefore, the objective of this work was to verify which the influence of the physical activity (treadmill workout) in the ultrastructural, in the in the neuronal density (neurons/mm2) and in the profile area of the cellular body (µm2) of the myenteric neurons of the jejunum of rats with aging. For so much, 45 Wistar rats were used and they were divided in three groups: C (controls with six months), S (sedentary with 12 months) and T (trained with 12 months) being used 5 animals for each technique/group. The whole mounts of the jejunum were stained with the NADH and NADPH histochemistry techniques to estimate the density and the profile area of the myenteric neurons. The results of the maximal exercise test (METs) they always bigger in the T group than S group. The weight of the animals of the T group was smaller than S group. The jejunum-ileum area was measured and it didn\'t present significant difference (P>0.05) among the animals of the C, s and T groups. Except for the basal membrane that it came less defined and of the periganglionic area that was more scattered in the animals of the S group, they were not identified ultrastructural alterations and in the arrangement of the myenteric plexus among the groups. The density of the NADH-diaphorase neurons was smaller (P<0.05) in the animals of the S group (67.76±3.7) in relation to the animals of the C (104.8±5.86) and T (95.18±7.18) groups. For the NADPH- diaphorase neurons, smaller neuronal density was observed in the S (32.32±1.7) and T (27.39±1.2) groups compared with the C group (44.53±4.5), but the significant differentiate didn\'t evidence among the S and T groups. The profile area (µm2) of the NADH-diaphorase neurons decreased in the S group (103.4±8.68) and increase in the T group (198.4±8.22) in relation to the C group (167±6.93). The profile area of the NADPH-diaphorase neurons was smaller statically among the T (129.9±9.55) and C (186.8±9.34) groups, but differences were not observed among these groups with the S group (157.3±3.64). However, the observed alterations indicate little are the influences of the aging in animals with 12 months age.

<p>After drinking water, the fluid quickly leaves the stomach thereby creating a hypotonic luminal environment in the duodenum. This in turn constitutes a potential threat to the integrity of the duodenal epithelium. It therefore seems highly likely that luminal hypotonicity activates physiological mechanisms that aim to increase luminal osmolality. One such physiological mechanism may be to increase mucosal permeability thereby facilitating the transport of osmolytes into the lumen.</p><p>A draw-back of performing experiments in anesthetized animals is that surgery <i>per se</i> depresses gut functions, such as peristalsis, by mechanisms involving endogenous prostaglandins. In this thesis it is shown that inhibition of cyclooxygenase-2 (COX-2), in animals subjected to an abdominal operation, restore and/or improve duodenal functions such as motility, mucosal bicarbonate secretion, hypotonicity-induced increase in mucosal permeability and the osmolality-adjusting capability.</p><p>Experiments revealed that the stomach is resistant to hypotonic challenge while the jejunum is more sensitive to hypotonicity-induced increase in mucosal permeability than the duodenum. The hypotonicity-induced increase in duodenal mucosal permeability is not due to injury but possibly reflects physiological dilatation of paracellular shunts.</p><p>Luminal perfusion of the duodenum with an isotonic solution lacking Cl^- decreased bicarbonate secretion while the lack of luminal Na⁺ increased mucosal permeability. Stimulation of bicarbonate secretion by COX-2 inhibition is to a large extent dependent on luminal Cl^- while that induced by vasoactive intestinal peptide is not.</p><p>The hypotonicity-induced increase in mucosal permeability involves the release and action of serotonin (5-HT) on 5-HT₃ and 5-HT₄ receptors and stimulation of enteric nerves strongly implicating physiological regulation of this process.</p>

After drinking water, the fluid quickly leaves the stomach thereby creating a hypotonic luminal environment in the duodenum. This in turn constitutes a potential threat to the integrity of the duodenal epithelium. It therefore seems highly likely that luminal hypotonicity activates physiological mechanisms that aim to increase luminal osmolality. One such physiological mechanism may be to increase mucosal permeability thereby facilitating the transport of osmolytes into the lumen. A draw-back of performing experiments in anesthetized animals is that surgery per se depresses gut functions, such as peristalsis, by mechanisms involving endogenous prostaglandins. In this thesis it is shown that inhibition of cyclooxygenase-2 (COX-2), in animals subjected to an abdominal operation, restore and/or improve duodenal functions such as motility, mucosal bicarbonate secretion, hypotonicity-induced increase in mucosal permeability and the osmolality-adjusting capability. Experiments revealed that the stomach is resistant to hypotonic challenge while the jejunum is more sensitive to hypotonicity-induced increase in mucosal permeability than the duodenum. The hypotonicity-induced increase in duodenal mucosal permeability is not due to injury but possibly reflects physiological dilatation of paracellular shunts. Luminal perfusion of the duodenum with an isotonic solution lacking Cl- decreased bicarbonate secretion while the lack of luminal Na+ increased mucosal permeability. Stimulation of bicarbonate secretion by COX-2 inhibition is to a large extent dependent on luminal Cl- while that induced by vasoactive intestinal peptide is not. The hypotonicity-induced increase in mucosal permeability involves the release and action of serotonin (5-HT) on 5-HT3 and 5-HT4 receptors and stimulation of enteric nerves strongly implicating physiological regulation of this process.

Die Stamm- und Vorläuferzellen, im Weiteren als Progenitoren bezeichnet, des humanen Darms treten seit einigen Jahrzehnten immer stärker in den Fokus der Forschung. Mit der Entdeckung von Progenitorzellen im zentralen Nervensystem in den 60er Jahren des 20. Jahrhunderts kamen auch Bestrebungen auf, im peripheren Nervensystem nach Progenitoren zu suchen. Bald darauf, zu Beginn des 21. Jahrhunderts, wurden Sie entdeckt. Diese Population von Zellen bietet eine vielversprechende Möglichkeit, aus adultem Darmgewebe Progenitorzellen zu isolieren und diese therapeutisch, bei einer Vielzahl gastroenterologischer Erkrankungen, autolog einzusetzen. Derzeit werden auch andere mögliche Stamm- und Vorläuferzellen evaluiert. Die vorliegende Arbeit liefert einen wichtigen Beitrag zur Charakterisierung humaner, enterischer, neuraler Progenitorzellen. Dies ist essentiell für eine mögliche, klinische Translation. Es gelang, die in vitro Kulturbedingungen der isolierten, humanen Zellen durch Wachstumsfaktorenzugabe und Supplemente zu verbessern und ermöglicht so auch ein besseres Verständnis der in vivo-Situation. Weiterhin wurde das sich verändernde enterische Nervensystem des humanen Darms, in verschiedenen Altersstufen, spezifisch isoliert und analysiert. Es konnten neuartige Befunde zum Verlust von neuronalen Zellen im Allgemeinen und der charakteristische Verlust von NOS-Neuronen im Speziellen erhoben werden. Erstmals beobachtet wurde die Erhöhung der Genexpression für Gliazellen im gealterten ENS. Die gewonnen Erkenntnisse wurden weiterhin in einer in vivo-Transplantationsstudie angewendet. In ein Mausmodell mit einem chemisch geschädigten Darmnerensystem wurden postnatale, humane Progenitoren eingebracht und es gelang der Beweis einer verbesserten Funktionalität durch Integration von neugebildeten Neuronen, Glia und Muskelzellen.

Τα κύτταρα της νευρικής ακρολοφίας είναι ένας πολυδύναμος πληθυσμός βλαστικών κυττάρων που δημιουργείται στη ραχιαία πλευρά του νευρικού σωλήνα των σπονδυλωτών κατά τη διάρκεια της νευριδίωσης. Μετά τη δημιουργία τους, τα κύτταρα της νευρικής ακρολοφίας μεταναστεύουν σε ολόκληρο το έμβρυο, ακολουθώντας συγκεκριμένα μονοπάτια, συνεισφέροντας στη δημιουργία μιας μεγάλης ποικιλίας δομών, όπως νευρικά και γλοιακά κύτταρα του περιφερικού νευρικού συστήματος (ΠΝΣ), μελανοκύττρα, δομές που συμβάλλουν στο σκελετό του κρανίου και του προσώπου κλπ. Η δημιουργία, η αυτο- ανανέωση και η διαφοροποίηση των κυττάρων της νευρικής ακρολοφίας απαιτούν το συντονισμό των διεργασιών του κυτταρικού πολλαπλασιασμού και της κυτταρικής διαφοροποίησης. Η αδυναμία συντονισμού των παραπάνω διαδικασιών οδηγεί στην εμφάνιση ασθενειών στον άνθρωπο (neurocristopathies). Η Geminin είναι ένα μόριο που έχει την ικανότητα να ρυθμίζει την πρόοδο του κυτταρικού κύκλου, αλληλεπιδρώντας με τον παράγοντα αδειοδότησης της αντιγραφής Cdt1, και τη διαφοροποίηση, μέσω της αλληλεπίδρασής της με μεταγραφικούς παράγοντες και πρωτεΐνες αναδιαμόρφωσης της χρωματίνης. Προηγούμενες μελέτες του εργαστηρίου μας έχουν αναδείξει τη Geminin ως ένα σημαντικό ρυθμιστή των διαδικασιών της αυτο- ανανέωσης και διαφοροποίησης στα πρόδρομα νευρικά κύτταρα στον αναπτυσσόμενο φλοιό. Προκειμένου να κατανοήσουμε τους μηχανισμούς που ελέγχουν την αυτο-ανανέωση και τη διαφοροποίηση των πολυδύναμων κυττάρων της νευρικής ακρολοφίας και να κατανοήσουμε το μοριακό μηχανισμό ασθενειών στον άνθρωπο που σχετίζονται με την απορρύθμιση του ελέγχου της ι κανότητας αυτο-ανανέωσης και διαφοροποίησης των πολυδύναμων κυττάρων της νευρικής ακρολοφίας μελετήσαμε το ρόλο της Geminin στη δημιουργία, την αυτο-ανανέωση, τον καθορισμό και τη διαφοροποίηση των κυττάρων της νευρικής ακρολοφίας. Προς αυτή την κατεύθυνση πραγματοποιήθηκαν τόσο in vivo όσο και in vitro πειράματα, χρησιμοποιώντας ζωικά μοντέλα τα οποία δημιουργήθηκαν από το εργαστήριο μας και στα οποία το γονίδιο της Geminin είχε αδρανοποιηθεί ειδικά στα κύτταρα της νευρικής ακρολοφίας. Τα αποτελέσματά μας έδειξαν ότι η απουσία της Geminin οδηγεί στη δημιουργία εμβρύων με σοβαρές μορφολογικές αλλοιώσεις, που κατά τα πρώιμα αναπτυξιακά στάδια χαρακτηρίζονται από την απουσία της δομής του μεσεγκεφάλου και των βραγχιακών τόξων και σε μεταγενέστερα αναπτυξιακά στάδια εμφανίζουν σοβαρή κρανιοπροσωπική δυσμορφία, με κατάληξη το θάνατο των εμβρύων, λίγες ημέρες πριν γεννηθούν. Επιπλέον, κατά τα πρώιμα αναπτυξιακά στάδια παρατηρήθηκαν σοβαρές αλλοιώσεις σε δομές που προέρχονται από τη νευρική ακρολοφία, όπως είναι τα κρανιακά και τα ραχιαία γάγγλια, οι γναθικές προεκβολές και τα πρόδρομα κύτταρα του εντερικού νευρικού συστήματος. Η μείωση του πληθυσμού των πρόδρομων κυττάρων του εντερικού νευρικού συστήματος (ΕΝΣ) οδήγησε στη δημιουργία ενός αγαγγλιονικού εντέρου, το οποίο παρομοιάζει με το φαινότυπο του ΕΝΣ στη νόσο Hirschsprung στον άνθρωπο. Η ιστοειδική αδρανοποίηση της Geminin οδήγησε στη μείωση των αδιαφοροποίητων κυττάρων νευρικής ακρολοφίας που δημιουργούνται στην αυχενική περιοχή του νευρικού σωλήνα και στην είσοδο μικρότερου αριθμού κυττάρων νευρικής ακρολοφίας στον γαστρεντερικό σωλήνα κατά τα πρώτα στάδια του αποικισμού του. Μελέτη των εντερικών κυττάρων νευρικής ακρολοφίας έδειξε ότι η αποσιώπηση της Geminin προκάλεσε την αύξηση της απόπτωσης κατά τις ηλικίες Ε9.5 και Ε10.5 και τη μείωση του κυτταρικού πολλαπλασιασμού τους κατά την ηλικία Ε9.5. Σε συνδυασμό με τη μειωμένη ικανότητα που δείχνουν τα πρόδρομα εντερικά κύτταρα να αυτο-ανανεώνονται, τα αποτελέσματά μας προτείνουν ότι η Geminin έχει σημαντικό ρόλο στην αυτο-ανανέωση και την επιβίωση των πρόδρομων κυττάρων του ΕΝΣ. Επιπλέον, η απουσία της Geminin οδηγεί στη μείωση των κυττάρων που έχουν καθορισμένη μοίρα και εκφράζουν τους δείκτες των πρόδρομων εντερικών κυττάρων Phox2b, Ret και Mash1, ενώ τα κύτταρα αυτά απουσία της Geminin παρουσιάζουν μειωμένη παραγωγή νευρικών κυττάρων, κατά την έναρξη της νευρωνικής διαφοροποίησης. Συμπερασματικά, τα αποτελέσματά μας αναδεικνύουν τη Geminin ως ένα σημαντικό μόριο κατά τη δημιουργία των πολυδύναμων κυττάρων της νευρικής ακρολοφίας. Επίσης η Geminin είναι απαραίτητη για τη δημιουργία των κυττάρων της νευρικής ακρολοφίας που αποικίζουν το γαστρεντερικό σωλήνα, ενώ ρυθμίζει την επιβίωση και την αυτο-ανανέωσή τους, καθώς και τη μετάβασή τους από την αρχικά αδιαφοροποίητη/πολυδύναμη κατάσταση στην εντερική αναπτυξιακή μοίρα. Επιπλέον η απουσία της Geminin δημιουργεί μύες οι οποίοι μιμούνται τη νόσο του Hirschsprung και αποτελούν ένα σημαντικό ζωικό μοντέλο για τη μελέτη των μηχανισμών της μοριακή παθογένειας της νόσου αλλά και στην εύρεση νέων θεραπειών. / The neural crest is a multipotent cell population that is formed at the dorsal neural tube of vertebrate embryos during neurulation. After their formation, neural crest cells (NCCs) delaminate from the neural tube and migrate throughout the embryo following specific pathways, and give rise to a wide variety of structures, such as neural and glial cells of the peripheral nervous system (PNS), melanocytes, structures of the craniofacial skeleton, etc. Neural crest formation, self-renewal and differentiation require the coordination of proliferation and differentiation. Deregulation of these processes results in developmental diseases in humans, known as neurocristopathies. Geminin is a molecule that has the ability to regulate cell cycle progression and differentiation, through interactions with the licensing factor Cdt1, transcription factors and chromatin remodeling factors. Previous studies from our laboratory have shown that Geminin is an important regulator of self-renewal and differentiation of early cortical progenitors. In order to understand the mechanisms that control self-renewal and differentiation of multipotent neural crest cells (NCCs) and gain insight into the molecular mechanism of human diseases, we studied the role of Geminin in the formation, self-renewal and differentiation of NCCs. Towards this direction, we performed in vivo and in vitro experiments, using animal models that have been generated in our laboratory and allow the conditional inactivation of Geminin in neural crest cells. Our results showed that deletion of Geminin causes severe morphological malformations in embryos that are characterized by the absence of midbrain, branchial arches and severe craniofacial malformation. Mutant embryos are dying a few days before birth. Moreover, during early embryonic development, the neural crest-derived structures, such as cranial and dorsal root ganglia, the maxillary and the mandibular components, and enteric progenitor cells, were severely affected. The decrease of enteric neural crest cells resulted in the formation of aganglionic gut that resembles with the phenotype of Hirschsprung disease. The conditional inactivation of Geminin resulted in the decreased formation of naïve vagal neural crest cells, while enteric neural crest cells were dramatically reduced. Geminin deficient enteric neural crest sells show increased apoptosis at E9.5 and E10.5, and decreased cell proliferation at E9.5. These findings, combined with the decreased self-renewal capacity of enteric progenitor cells (EPCs) in vitro, suggest that Geminin is important for the self-renewal and the survival of ENS progenitor cells. In addition, deletion of Geminin resulted in decreased committed enteric neural crest cells, that express enteric progenitor markers Phox2b, Ret and Mash1. In conclusion, our results highlight Geminin as an important molecule during the formation of multipotent neural crest cells. Geminin is required for the formation of vagal neural crest cells that colonize the gastrointestinal tract, and regulates survival and selfrenewal of these cells, as well as their transition from a multipotent state to the committed enteric lineage of progenitor cells. Moreover, conditional inactivation of Geminin leads to Hirschsprung-like phenotype that could be used as model organisms to study disease pathogenesis and help in the discovery of new therapies.

Normal intestinal functions are coordinated by enteric neurons within the enteric nervous system (ENS). In the embryonic and neonatal gut, enteric neuron survival is dependent on the expression of glial cell line-derived neurotrophic factor (GDNF) from its targets of innervation - the intestinal smooth muscle cells (ISMC). In the inflamed adult intestine, enteric neuron loss is immediately followed by ISMC proliferation, resulting in severe disruption of normal intestinal functions. Although GDNF can support the survival of postnatal enteric neurons, whether adult ISMC can secrete GDNF and support neuron survival is unclear. Results from qPCR analysis showed that freshly isolated adult ISMC have acquired the ability to express GDNF at the onset of proliferation, in vitro. Western blot analysis indicates that GDNF continues to be upregulated in ISMC at Passage 2 (P2), but its expression is decreased after long periods of proliferation at Passage 10 (P10). A neuron survival bioassay suggests that GDNF expression is correlated with enteric neuron survival. Results showed that P2 ISMC or conditioned media (CM) - but not P10 ISMC and CM, significantly increased enteric neuron survival. In subsequent experiments, the RET tyrosine kinase inhibitor vandetanib was used to block GDNF receptor-ligand interactions, and anti-GDNF neutralizing antibody was used to sequester soluble GDNF within the culture media. Both methods were successful at decreasing myenteric neuron survival. Furthermore, abolishing GDNF expression in P2 ISMC with GDNF siRNA also resulted in a decreased myenteric neuron survival. The above observations suggest that ISMC-derived GDNF is important in supporting myenteric neuron survival in vitro. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2012-09-28 09:43:23.968

Parkinson’s disease is a neurodegenerative disease resulting primarily from loss of dopaminergic innervation in the striatum subsequent to cell loss in the substantia nigra pars compacta. The abnormal accumulation of the normal pre-synaptic protein α-synuclein (αsyn) forms intraneuronal inclusions known as Lewy neurites and Lewy bodies. The origins of central Lewy pathology have been suggested to lie in the enteric nervous system, ascending through the vagus nerve to the dorsal motor nucleus of the vagus. To ascertain gastrointestinal regions most likely to be the source of central Lewy pathology, αsyn expression was evaluated in the neural elements of gastrointestinal regions receiving the densest vagal innervation. The vermiform appendix was found to have the densest αsyn-immunoreactive innervation in all layers of the gut wall. In addition, macrophages in the appendiceal mucosa were laden with αsyn within lysosomes, consistent with attempts to prevent the spread of disease or to correct synaptic dysfunction.