Physiology of Vomiting

Summary

Vomiting in dogs is a common reason for veterinary visits, with various potential causes such as dietary issues, infections, and systemic diseases like pancreatitis or kidney failure. The diagnosis and treatment can be challenging due to the multiple underlying conditions. Vomiting is controlled by the emetic center in the brain, which responds to both central and peripheral stimuli, including toxins and motion sickness. Receptors like NK1, located in both the emetic center and chemoreceptor trigger zone, play a crucial role in the vomiting reflex, highlighting the complexity of treating this condition.

Takeaways

• 😀 Vomiting is a common reason for dog owners to visit the veterinarian, with an average of 28 vomiting dogs seen per month.
• 😀 Vomiting in dogs can be caused by a variety of medical conditions, including dietary indiscretion, gastritis, gastroenteritis, parvovirus, motion sickness, GI obstruction, pancreatitis, and renal disease.
• 😀 Diagnosis and treatment of vomiting in dogs can be challenging due to the many potential underlying conditions and lack of a standard treatment approach.
• 😀 Veterinarians may suggest different approaches for treating vomiting, including watching and waiting, withholding food and water, feeding a bland diet, trying over-the-counter remedies, or bringing the dog in for veterinary care if symptoms persist.
• 😀 Prescription medications may be prescribed for vomiting, with varying degrees of success while the underlying condition is explored.
• 😀 Vomiting in dogs is controlled by the emetic center in the brainstem, where all vomiting stimuli converge.
• 😀 Vomiting stimuli travel through two main pathways to the emetic center: central and peripheral. Central stimuli come from higher brain centers, while peripheral stimuli may travel via neural afferents or the chemoreceptor trigger zone (CRTZ).
• 😀 Different conditions cause vomiting signals to travel to the emetic center via either the central or peripheral pathways, and some conditions may involve both pathways.
• 😀 The chemoreceptor trigger zone (CRTZ) plays a crucial role in detecting circulating toxins and signaling the emetic center to initiate vomiting.
• 😀 The NK1 receptor is a key player in the vomiting reflex, with a high concentration of NK1 receptors in both the emetic center and the CRTZ. Substance P, a neurotransmitter, binds to these receptors to trigger the vomiting cascade.

Q & A

What is the most common reason owners bring their dogs to the veterinarian?

Vomiting is one of the most common reasons that dog owners bring their dogs to the veterinarian.

What range of medical conditions can cause vomiting in dogs?

Vomiting in dogs can be caused by a variety of conditions including dietary indiscretion, gastritis, gastroenteritis, parvovirus, motion sickness, gastrointestinal obstruction, pancreatitis, and renal disease.

Why is diagnosing the cause of vomiting in dogs challenging?

Diagnosis is challenging because vomiting can be caused by a wide range of conditions, each with its own unique symptoms and underlying mechanisms, making it difficult to pinpoint the exact cause.

What are some common approaches to treating vomiting in dogs?

Common treatment approaches include withholding food and water, feeding a bland diet, trying over-the-counter remedies, or bringing the dog in for veterinary care if vomiting persists or worsens.

What is the emetic center, and what role does it play in vomiting?

The emetic center is a cluster of brainstem nuclei responsible for controlling the physical reflex of vomiting. It is where all vomiting signals ultimately converge before initiating the vomiting response.

How do the central and peripheral pathways contribute to vomiting?

Stimuli in the central pathway travel directly from higher brain centers to the emetic center, while stimuli in the peripheral pathway reach the emetic center either directly via neural afferents or indirectly through the chemoreceptor trigger zone (CRTZ).

What is the chemoreceptor trigger zone (CRTZ), and how does it relate to vomiting?

The CRTZ is an area outside the blood-brain barrier that detects circulating toxins in the bloodstream and signals the emetic center to initiate vomiting. It plays a key role in the peripheral pathway of vomiting.

What are the receptor types involved in vomiting signaling in the CRTZ?

The CRTZ contains seven known receptor types that mediate the vomiting signal: neurokinin 1 (NK1), serotonin (5-HT3), adrenergic, dopaminergic, muscarinic, and histamine receptors.

How does substance P contribute to the vomiting reflex?

Substance P, a neurotransmitter produced by various tissues, binds to NK1 receptors in the emetic center, triggering a cascade of events that results in vomiting.

Why is the treatment of vomiting in dogs so challenging?

Treatment is challenging because vomiting can be triggered by various conditions, and the multiple pathways involved in the vomiting reflex mean that different treatments may be needed depending on the underlying cause.