The brain-gut axis
What hypothalamic nucleus integrates peripheral hormonal signals and lies near the third ventricle, allowing access to circulating factors?
Arcuate nucleus
What antiemetic class is especially useful for chemotherapy-induced and parvoviral vomiting due to their action on vagal afferents?
5-HT₃ antagonists
ondansetron
All stimulatory pathways for gastric acid secretion converge on what parietal cell enzyme.
H⁺/K⁺ ATPase proton pump.
What drug improves esophageal, gastric, small intestinal, and colonic motility by enhancing acetylcholine release through serotonergic receptor activation, addressing pathologic hypomotility?
Cisapride
What hepatoprotective agent supports glutathione synthesis and methylation reactions, counteracting oxidative injury rather than reversing underlying hepatic disease?
S-adenosylmethionine (SAMe)
What adipose-derived hormone signals long-term energy sufficiency and suppresses appetite through activation of anorexigenic neurons?
Leptin
What neuropeptide is considered the final common mediator of emesis in both central and peripheral pathways?
Substance P
What class of drugs irreversibly inhibit the final common pathway of acid secretion and provide the most potent acid suppression?
proton pump inhibitors
What osmotic laxative is metabolized by colonic bacteria to organic acids that increase intraluminal water content while also trapping ammonia in the colon, making it useful in two distinct disease processes?
Lactulose
What therapeutic agent enhances bile salt–dependent bile flow after enterohepatic circulation, inhibits cholesterol synthesis via feedback, and promotes absorption of fat-soluble vitamins?
ursodeoxycholic acid (UDCA); ursodiol
What molecule is necessary for normal insulin action and influences lipid and carbohydrate metabolism rather than directly stimulating appetite?
Adiponectin
What antiemetic blocks NK-1 receptors and is effective against both central and peripheral causes of vomiting?
Maropitant
What macrolide antibiotic promotes gastric emptying by acting as a motilin receptor agonist?
erythromycin
By activating peripheral μ-opioid receptors in the intestinal wall, what drug reduces secretory diarrhea but may cause CNS toxicity in dogs with defective P-glycoprotein efflux?
loperamide
What nondigestible dietary substrates improve gastrointestinal health by selectively stimulating growth and activity of beneficial colonic bacteria rather than providing live organisms?
prebiotics
What gastric hormone rises during fasting and directly opposes leptin’s effects at the hypothalamus?
Ghrelin
Over 90% of what neurotransmitter is located in the GI tract?
Serotonin
What prostaglandin analog is most effective for NSAID-induced ulcer prevention but is contraindicated in pregnancy?
misoprostol
What neurotransmitter is the primary excitatory mediator of gastrointestinal smooth muscle contraction, and impaired release contributes to pathologic hypomotility states?
acetylcholine
In portosystemic shunting, accumulation of what neurotoxin alters astrocyte metabolism, increases glutamine production, and disrupts neurotransmission by interfering with blood–brain barrier amino acid transport?
What structure lies outside the blood–brain barrier and detects circulating toxins, drugs, and metabolic disturbances?
Chemoreceptor trigger zone (CTZ)
What antiemetic class blocks dopamine receptors in the CTZ and also increases acetylcholine release in the upper GI tract? Give an example.
Dopamine antagonists
Metoclopramide
What management strategy improves the efficacy of pancreatic enzyme supplementation by preventing acid-mediated degradation of lipase?
concurrent gastric acid suppression
What class of antidiarrheal drugs is rarely recommended due to systemic muscarinic blockade leading to ileus, urinary retention, and tachycardia?
anticholinergics
What drug therapy improves appendicular muscle strength in dogs with myasthenia gravis–associated megaesophagus but often fails to restore esophageal or pharyngeal function?
Pyridostigmine