The availability of murine genetic models is extremely advantageous to studying gastrointestinal function, but the benefits afforded by studying enteric neurons in mice has been hindered by their accessibility. Fetal (E13) and 2 day post-natal (P2) enteric neuron cell lines (IM-FEN and IM-PEN, respectively) were recently developed from the H-2Kb-tsA58 immortomouse. Our goal was to identify the electrophysiological properties of these cell lines and clarify their utility as a model of enteric neurons. IM-PEN cells stained positively for the neuron specific markers βIII-tubulin and PGP9.5 and were negative for the glial cell marker S100. Detection of mRNA for TRPA1, TRPV1, ClCa1, KCa3.1, NaV1.3 and NaV1.9 were present while CaV2.2 and TASK1 were very faint. No significant difference was observed in the passive membrane properties of IM-FEN and IM-PEN. The cells had depolarized resting membrane potentials -29.8 ± 0.9mV (n=30) and high input resistances ranging from 552 ± 104MΩ (IM-FEN, n=6) to 728 ± 128MΩ (IM-PEN, n=20). xiv In current clamp, hyperpolarizing current was given to obtain a holding potential of -60mV or -80mV, yet neither IM-FEN (n=6) nor the IM-PEN cells (n=20) were able to generate action potentials in response to depolarizing pulses. In whole cell voltage clamp depolarization induced an inward current which was identified as an L-type Ca2+ channel. Niflumic acid inhibited the outward current as well as the tail currents indicating a ClCa current supporting the mRNA data. A volume sensitive chloride channel was also identified that was DCPIB sensitive (n=7) and removed when chloride was replaced with gluconate (n=4), displaying characteristics of ICl,swell. As a result IM-PEN cells had a high chloride conductance resulting in a depolarized membrane potential, which is a characteristic of immature neurons. The transcription factor MASH1 has been found to be required for enteric neuron differentiation. Transfection of MASH1 after 4 and 8 days did not alter the electrophysiological characteristics of IM-PEN (n=6). We conclude that IM-PEN may represent immature enteric neurons and are a useful model to examine the effect of factors required for the development of enteric neurons.

Orientador: José Ricardo de Arruda Miranda / Resumo: O estado hiperglicêmico está relacionado com alterações fisiológicas em todo o organismo no diabete. É conhecido a recorrência de distúrbios gastrintestinais em indivíduos diabéticos. Estudos sobre alterações da motilidade gastrintestinal em diabéticos mostram danos em neurônios entéricos e na parede gástrica. Há uma lacuna no conhecimento sobre a relação entre níveis glicêmicos, motilidade gastrintestinal e neurônios entéricos. Portanto o objetivo foi analisar a atividade de contração, esvaziamento gástrico e trânsito oro-cecal em ratos com modelos de diabete grave e moderado e avaliar a integridade da parede gástrica e dos neurônios entéricos. Os animais foram induzidos ao diabete com Streptozotocin (STZ) (diabete moderado: 100mg/kg; glicemia de jejum 6,6-16,5 mmol/L) e (diabete grave: 50mg/kg glicemia de jejum> 16,5mmol/L). A Biosusceptometria AC (BAC) aferiu a contratilidade gástrica, quantificados por frequência e meia-largura da banda em ciclos por minuto. Assim como o esvaziamento gástrico (EG) e o trânsito oro-cecal (TOC), analisados por tempo médio de EG e tempo médio de chegada ao ceco, respectivamente. A atividade elétrica gástrica foi aferida por eletrogastrograma (EGG). A histologia da parede gástrica foi realizada por hematoxilina-eosina e mensurada a espessura da mucosa e das musculares longitudinal e circular, do corpo do estômago. Os neurônios colinérgicos (ChAT) e nitrérgicos (nNOS) do plexo mioentérico do corpo do estômago foram marcados por imuno-histoquím... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The hyperglycemic state is related to physiological changes throughout the body in diabetes. Recurrence of gastrointestinal disorders in diabetic individuals is known. Studies on changes in gastrointestinal motility in diabetics show damage to enteric neurons and the gastric wall. Few are the knowledge about the relationship among glycemic levels, gastrointestinal motility and enteric neurons. Therefore, the aim was to analyze the activity of contraction, gastric emptying and oro-cecal transit in rats with mild and severe diabetes models and to evaluate the integrity of the gastric wall and the enteric neurons. The animals were diabetic with Streptozotocin (STZ) (moderate diabetes: 100mg/kg; fasting blood glucose 6.6-16.5 mmol/L) and (severe diabetes: 50mg/kg fasting blood glucose>16.5mmol/L). AC biosusceptometry (ACB) measured gastric contractility, quantified per frequency and half-band width in cycles per minute. As well as gastric emptying (EG) and oro-cecal transit, analyzed by mean time of EG and mean time of arrival to the cecum, respectively. Gastric electrical activity was measured by electrogastrogram (EGG). The histology of the gastric wall was performed by hematoxylin-eosin and measured the thickness of the mucosa and the longitudinal and circular muscles of the stomach body. The cholinergic (ChAT) and nitrergic (nNOS) neurons of the myenteric plexus of the stomach body were marked by immunohistochemistry, the density of neurons per ganglion and neural area profil... (Complete abstract click electronic access below) / Doutor

Neste trabalho foram analisados os efeitos do BBG nos neurônios mioentéricos imunorreativos ao receptor P2X7 no íleo de ratos submetidos à isquemia e reperfusão (I/R). A isquemia intestinal foi obtida pela oclusão dos vasos ileais por 45 minutos, com reperfusão de 0 hora (h), 24 h e 14 dias. O BBG foi aplicado nos grupos I/R 24 h e I/R 14 dias nas dosagens de 50 e 100 mg/Kg. O grupo I/R 0 h é o grupo sem reperfusão. Os tecidos foram preparados para análises de duplas marcações, western blotting, histoquímica da mieloperoxidase, histologia e motilidade intestinal. Os resultados demonstraram a presença do receptor P2X7 nos neurônios mioentéricos. Houve uma diminuição da densidade e da área do perfil dos neurônios mioentéricos nos grupos I/R e nos grupos com o BBG houve uma recuperação dos neurônios. Nos grupos I/R houve aumento na expressão do receptor P2X7 e no número de neutrófilos e diminuição da motilidade. Os resultados sugerem que a I/R afetou os neurônios mioentéricos e que o BBG possa ter atenuado os efeitos da I/R, demonstrando uma provável neuroproteção. / We analyzed the effects of BBG antagonist on the P2X7 receptor and rats ileum enteric neurons subjected to I/R. Intestinal ischemia was obtained by ileal vessels obstruction for 45 minutes, followed by reperfusion of 0 h, 24 h and 14 days. The BBG was applied in I/R 24 h and 14 days groups in dosages of 50 and 100 mg/kg. The I/R 0 h is the group without reperfusion. Tissues were prepared by double labeling, western blotting, myeloperoxidase reaction, histology and intestinal motility analyzes. Our results demonstrated the presence of the P2X7 receptor in myenteric neurons. There was a decrease in density and in the area of the cell body profile of the myenteric neurons in the I/R groups and recovery in the BBG groups. In I/R groups there was an increase in the expression of P2X7 receptor and in the number of neutrophils and there was a decrease in intestinal motility and recover in the BBG groups. The results suggest that I/R affect the myenteric neurons and that the BBG may have attenuated the effects of ischemia, thus demonstrating a possible neuroprotection.

Neste trabalho foram analisados os efeitos do BBG nos neurônios mioentéricos imunorreativos ao receptor P2X7 no íleo de ratos submetidos à isquemia e reperfusão (I/R). A isquemia intestinal foi obtida pela oclusão dos vasos ileais por 45 minutos, com reperfusão de 0 hora (h), 24 h e 14 dias. O BBG foi aplicado nos grupos I/R 24 h e I/R 14 dias nas dosagens de 50 e 100 mg/Kg. O grupo I/R 0 h é o grupo sem reperfusão. Os tecidos foram preparados para análises de duplas marcações, western blotting, histoquímica da mieloperoxidase, histologia e motilidade intestinal. Os resultados demonstraram a presença do receptor P2X7 nos neurônios mioentéricos. Houve uma diminuição da densidade e da área do perfil dos neurônios mioentéricos nos grupos I/R e nos grupos com o BBG houve uma recuperação dos neurônios. Nos grupos I/R houve aumento na expressão do receptor P2X7 e no número de neutrófilos e diminuição da motilidade. Os resultados sugerem que a I/R afetou os neurônios mioentéricos e que o BBG possa ter atenuado os efeitos da I/R, demonstrando uma provável neuroproteção. / We analyzed the effects of BBG antagonist on the P2X7 receptor and rats ileum enteric neurons subjected to I/R. Intestinal ischemia was obtained by ileal vessels obstruction for 45 minutes, followed by reperfusion of 0 h, 24 h and 14 days. The BBG was applied in I/R 24 h and 14 days groups in dosages of 50 and 100 mg/kg. The I/R 0 h is the group without reperfusion. Tissues were prepared by double labeling, western blotting, myeloperoxidase reaction, histology and intestinal motility analyzes. Our results demonstrated the presence of the P2X7 receptor in myenteric neurons. There was a decrease in density and in the area of the cell body profile of the myenteric neurons in the I/R groups and recovery in the BBG groups. In I/R groups there was an increase in the expression of P2X7 receptor and in the number of neutrophils and there was a decrease in intestinal motility and recover in the BBG groups. The results suggest that I/R affect the myenteric neurons and that the BBG may have attenuated the effects of ischemia, thus demonstrating a possible neuroprotection.

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