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Gastroduodenal resistance and neural mechanisms involved in saline flow decrease elicited by acute blood volume
J R Craça1, F de A Gondim, D I Cavalcante
1Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Fortaleza, Brasil.
Summary
Blood volume expansion increases gastroduodenal resistance to fluid flow in rats. The pylorus and duodenum are key sites, with alpha-adrenergic and vagal mechanisms involved in regulating this response.
Area of Science:
- Physiology
- Gastroenterology
- Cardiovascular Physiology
Background:
- Previous studies demonstrated blood volume expansion reduces gastroduodenal (GD) saline flow in rats.
- The specific sites and neural mechanisms underlying this phenomenon require elucidation.
Purpose of the Study:
- To identify the resistance sites within the gastroduodenal tract responsible for flow reduction during blood volume expansion.
- To investigate the neural mechanisms mediating these changes in gastrointestinal perfusion.
Main Methods:
- Surgical creation of four distinct gut circuits (gastric, pyloric, duodenal, GD) in anesthetized rats.
- Perfusion of these circuits under controlled pressure with measurement of flow rate changes during normovolemia and blood volume expansion.
- Administration of pharmacological agents (prazosin, yohimbine, atropine, hexamethonium, propranolol) and vagotomy to assess neural involvement.
Main Results:
- Blood volume expansion significantly reduced perfusion flow in the GD, pyloric, and duodenal circuits, but not the gastric circuit.
- Prazosin and yohimbine blocked the expansion-induced reduction in duodenal flow, while vagotomy partially affected the pyloric response.
- Atropine, hexamethonium, and propranolol did not alter the observed flow changes.
Conclusions:
- Blood volume expansion elevates resistance to liquid flow within the gastroduodenal segment.
- The pylorus and duodenum are critical sites contributing to this increased resistance.
- Alpha-adrenergic pathways (blocked by prazosin and yohimbine) and vagal innervation play roles in modulating duodenal and pyloric resistance during volume expansion.