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Physiological enteric stimulation elicits cardiovascular reflexes in the rat
B S Pittam1, W R Ewart, F Appia
1Gastrointestinal Science Research Unit, London Hospital Medical College, United Kingdom.
The American Journal of Physiology
|September 1, 1988
Summary
Cardiovascular reflexes can be activated by stimulating stomach and liver receptors in rats. Vagal afferents mediate gastric reflexes, while hepatic reflexes involve different pathways, influencing heart rate and blood pressure.
Area of Science:
- Physiology
- Gastroenterology
- Cardiology
Background:
- Cardiovascular reflexes are crucial for maintaining homeostasis.
- Gastrointestinal receptors play a role in modulating cardiovascular function.
- Understanding these reflexes is vital for interpreting studies on sensory information processing.
Purpose of the Study:
- To establish parameters for activating cardiovascular reflexes via gastric and hepatic receptor stimulation in anesthetized rats.
- To investigate the role of vagal afferents in mediating these reflexes.
- To identify the specific adrenoreceptors involved in the cardiovascular responses.
Main Methods:
- Anesthetized rats were used to determine minimum effective intragastric volume and hepatic portal vein infusion rate for reflex activation.
- Subdiaphragmatic vagotomy was performed to assess the involvement of vagal afferents.
- Pharmacological antagonists were used to identify the role of alpha- and beta-adrenoreceptors.
Main Results:
- Minimum activation parameters: 4 ml intragastric volume and 0.3 ml/min hepatic portal vein infusion rate.
- Vagotomy affected gastric distension responses but not hepatic portal vein infusion responses, indicating vagal involvement in gastric reflexes only.
- Tachycardia was mediated by beta-adrenoreceptor stimulation, and the pressor response by alpha-adrenoreceptors.
Conclusions:
- Stimulation of gastric and hepatic receptors can activate cardiovascular reflexes in rats.
- Vagal afferents are specifically involved in gastric-cardiovascular reflexes, not hepatic-cardiovascular reflexes.
- The cardiovascular responses involve distinct alpha- and beta-adrenoreceptor pathways, highlighting the complexity of gastrointestinal-cardiovascular interactions.