Respiratory changes after intraarterial acetylcholine and abdominal concussion

Area of Science:

• Veterinary Physiology
• Gastrointestinal Physiology
• Respiratory Physiology

Background:

• Acetylcholine (ACh) is a neurotransmitter with diverse physiological effects.
• The role of gastrointestinal afferent pathways in respiratory control is not fully understood.
• Abdominal trauma can elicit reflex responses affecting respiration.

Purpose of the Study:

• To investigate the respiratory effects of intraarterial acetylcholine (ACh) administration in specific gastrointestinal arteries.
• To determine the involvement of the splanchnic nerves and muscarinic receptors in ACh-induced respiratory changes.
• To explore the potential link between gut smooth muscle contraction and respiratory apnea.

Main Methods:

• Respiratory parameters were monitored in 50 anesthetized dogs.
• Intraarterial injections of ACh were administered into various arteries, including mesenteric, splenic, gastric, hepatic, and pulmonary trunk.
• Splanchnic nerve sectioning and administration of atropine sulfate were performed.
• Abdominal blows were applied to observe respiratory responses.
• Gut smooth muscle contraction was recorded using intra-luminal balloons.

Main Results:

• Intraarterial ACh in mesenteric, splenic, and left gastric arteries induced expiratory apnea.
• This apnea was abolished by splanchnic nerve sectioning and reduced/abolished by atropine sulfate.
• ACh did not affect respiration when injected into the hepatic artery or pulmonary trunk.
• ACh injection into peripheral arteries, like the subclavian, caused respiratory stimulation.
• Abdominal blows produced similar expiratory apnea, suggesting a common origin in smooth muscle receptors.

Conclusions:

• Intraarterial ACh administration into specific gastrointestinal arteries triggers expiratory apnea in dogs.
• The splanchnic nerves and muscarinic receptors mediate this respiratory response.
• Gastrointestinal smooth muscle contraction appears to be a key factor in the observed apnea, potentially via visceral afferent pathways.