Alteration in gastric nerve fibers containing gastrin-releasing peptide in relation to the gastrin-producing cell population after truncal vagotomy in a rat model

Exclusão gastroduodenal e vagotomia troncular: repercussão no peso corporal e gastrinemia- estudo experimental em ratos

OBJETIVO: A obesidade mórbida é uma doença crônica que se acompanha de várias complicações médicas e de uma menor esperança de vida, prejudicando o aspecto físico, emocional, econômico e social. As pesquisas clínicas e experimentais são amplamente justificadas nesta doença, considerando-se que a opção de tratamento operatório é recente. As gastroplastias e as derivações gástricas são algumas das modalidades terapêuticas propostas e produzem uma grande câmara gástrica remanescente, que em algumas técnicas fica totalmente excluída do trânsito alimentar. As possíveis alterações deste segmento, transformado em apêndice do sistema digestório, representam um vasto campo para pesquisa. Tivemos como objetivo avaliar o peso e as alterações da dosagem de gastrina sérica do rato, após denervação vagal troncular subdiafragmática, com exclusão da câmara gástrica e duodeno do trânsito alimentar do animal. MÉTODO: Foi realizada vagotomia troncular e exclusão gastroduodenal em cem ratos, dos quais trinta puderam ser estudados. Eram ratos machos adultos (Rattus Norvegicus Albinus), da linhagem Wistar, com peso médio de 378,67 g. Este estudo foi complementado pela dosagem sérica de gastrina por radioimunoensaio com I125 e duplo anticorpo para gastrina. RESULTADOS: O peso de todos os ratos estudados diminuiu em média de 378,67 g para 285,83 g. Os trinta animais perderam em média 92,83 g (-24,52%). Houve diferenças significativas entre o peso inicial dos animais e o peso final (p< 0,001). A gastrina sérica também diminuiu em vinte e um dos trinta ratos operados, caindo de 59,68 pg/ml para 46,77 pg/ml em média, correspondendo a uma diminuição de 12,91 pg (-19,73%) entre as duas médias (p< 0,001). A análise estatística teve como objetivo avaliar se houve diminuição nas médias das variáveis: peso e gastrina, medidas antes e depois da operação proposta. Para avaliar as diferenças entre as médias, utilizou-se o teste estatístico do T-Student. CONCLUSÕES: Houve uma diminuição significativa do peso e da dosagem de gastrina sérica do animal.

Neurochemical coding and projection patterns of gastrin-releasing peptide-immunoreactive myenteric neurone subpopulations in the guinea-pig gastric fundus

The aim of this study was to characterise the projection and neurochemical coding patterns of gastrin-releasing peptide (GRP)-containing subpopulations of myenteric neurones in the guinea-pig gastric fundus. For this purpose, we used retrograde tracing with the dye DiI and immunohistochemistry against GRP, choline acetyltransferase (ChAT), enkephalin (ENK), substance P (SP) and neuropeptide Y (NPY). Cell counts revealed that 44% of the myenteric neurones were GRP-positive. Of the GRP-positive neurones, 92% were ChAT-positive and, hence, 8% were presumptively nitric oxide synthase positive (NOS). The GRP-positive subpopulations were ChAT/GRP (40% of all GRP neurones), ChAT/NPY/GRP (25%), ChAT/SP/GRP/+/-ENK (20%), ChAT/ENK/GRP (8%), NOS/NPY/GRP/+/-ENK (5%) and NOS/GRP (3%). The tracing experiments revealed the relative contributions of the various GRP-positive subpopulations to the innervation of the circular muscle and the mucosa. GRP immunoreactivity was detected in 46 and 38% of the DiI-labelled muscle and mucosa neurones, respectively. GRP was almost exclusively found in ascending ChAT-positive mucosa and muscle neurones. The populations encoded ChAT/SP/GRP/+/-ENK and ChAT/ENK/GRP projected predominantly to the circular muscle, whereas the ChAT/NPY/GRP and ChAT/GRP populations had primarily projections to the mucosa. GRP was colocalised with ChAT, ENK and/or SP in varicose nerve fibres innervating the circular muscle and the muscularis mucosae, whereas in the mucosal epithelium GRP was mainly present in nerve fibres containing ChAT and NPY. The data suggest that in the guinea-pig gastric fundus, the ChAT/SP/GRP/+/-ENK and ChAT/ENK/GRP neurones are ascending excitatory muscle motor neurones, whereas the ChAT/NPY/GRP and ChAT/GRP neurones are very likely involved in the regulation of mucosal functions.

Effect of cysteamine on gastric nerve fibers containing gastrin-releasing peptide in the rat

In rats, changes in gastric nerve fibers containing gastrin-releasing peptide (GRP) in cysteamine-induced duodenal ulcer were investigated in relation to the dynamics of gastrin-producing cells (G-cells). Marked increases in gastric acid secretion and serum gastrin level were observed from 2 h after the administration of cysteamine. The number of G-cells was significantly decreased from 2 h after the injection of cysteamine. Two and 4 h after the administration of cysteamine, the G-cells showed ultrastructural changes characterized by a markedly decreased number of secretory granules. Circulating GRP levels were significantly elevated from 2 h after the administration of cysteamine. In the control group given vehicle only, nerve fibers showing immunoreaction for GRP formed a fine network in the gastric wall and were densely distributed in the oxyntic mucosa, located close to capillaries and demonstrated varicosities that contained either small clear vesicles or GRP-immunopositive vesicles with large cores. Eight h after the administration of cysteamine, there was depleted GRP immunoreactivity, evidenced by a markedly decreased number of vesicles, with large electron-dense cores, in the oxyntic mucosa. These findings suggest that, in cysteamine-induced duodenal ulcer, alterations in gastric nerve fibers containing GRP may be related to hypergastrinemia.