Gastrointestinal drug screening: antiulcer, antiemetic, antidiarrheal and laxatives MCQs With Answer

Gastrointestinal drug screening: antiulcer, antiemetic, antidiarrheal and laxatives MCQs With Answer

Introduction: This quiz collection is designed for M.Pharm students specializing in pharmacological and toxicological screening methods focusing on gastrointestinal (GI) therapeutics. It covers experimental models, biochemical and histological endpoints, mechanisms of action, common positive controls, and interpretation of results for antiulcer, antiemetic, antidiarrheal and laxative screening. Questions emphasize practical screening protocols (e.g., pylorus ligation, ethanol/NSAID ulcer models, castor oil diarrhea, charcoal transit, emesis models), key biomarkers (gastric pH, ulcer index, mucin, MPO, prostaglandins), and regulatory/ethical considerations. These MCQs reinforce conceptual depth and experimental design needed to evaluate candidate GI drugs in preclinical research.

Q1. In the classical Shay pylorus ligation model for antiulcer screening in rats, which primary parameter is directly measured to assess antisecretory activity?

• Total gastric acid output (volume × acidity)
• Gastric mucosal thickness by histology
• Number of superficial erosions
• Plasma gastrin concentration

Correct Answer: Total gastric acid output (volume × acidity)

Q2. Which animal is most commonly used for emesis studies because it possesses a vomiting reflex similar to humans and is sensitive to chemotherapeutic emetogens?

• Ferret
• Rat
• Mouse
• Guinea pig

Correct Answer: Ferret

Q3. Castor oil induces diarrhea primarily through which biochemical mediator released in the intestine?

• Prostaglandin E2 (PGE2)
• Serotonin (5-HT)
• Histamine
• Bradykinin

Correct Answer: Prostaglandin E2 (PGE2)

Q4. Which assay is commonly used to quantify gastric mucus level as a protective factor in antiulcer studies?

• Alcian blue binding assay
• Bradford protein assay
• Thiobarbituric acid reactive substances (TBARS)
• ELISA for TNF-α

Correct Answer: Alcian blue binding assay

Q5. In screening for 5-HT3 receptor antagonists as antiemetics, which experimental stimulus is often used to provoke emesis mediated by serotonin release?

• Cisplatin administration
• Pilocarpine injection
• Acetic acid intraperitoneal
• Cold-water immersion

Correct Answer: Cisplatin administration

Q6. Which parameter is used to calculate the ulcer index in experimental gastric ulcer models?

• Number and severity (score) of ulcers per stomach
• Serum creatinine concentration
• Intestinal transit percentage of charcoal meal
• Fecal water content

Correct Answer: Number and severity (score) of ulcers per stomach

Q7. Loperamide’s antidiarrheal effect in animal models is primarily due to which mechanism?

• μ-opioid receptor agonism reducing intestinal motility
• Inhibition of prostaglandin synthesis
• Activation of fluid secretion via chloride channels
• Anticholinergic blockade of muscarinic receptors

Correct Answer: μ-opioid receptor agonism reducing intestinal motility

Q8. Which biochemical marker is commonly measured to estimate neutrophil infiltration and inflammation in gastric tissues?

• Myeloperoxidase (MPO) activity
• Alanine aminotransferase (ALT)
• Creatine kinase (CK)
• Alkaline phosphatase (ALP)

Correct Answer: Myeloperoxidase (MPO) activity

Q9. For laxative screening, the charcoal meal gut transit test evaluates which primary outcome?

• Percentage distance traveled by charcoal marker along small intestine
• Gastric acid secretion volume
• Colonic bacterial counts
• Serum electrolyte concentrations

Correct Answer: Percentage distance traveled by charcoal marker along small intestine

Q10. Which compound is most frequently used as a positive control (standard drug) in NSAID-induced gastric ulcer models when evaluating cytoprotective agents?

• Misoprostol
• Metoclopramide
• Loperamide
• Senna extract

Correct Answer: Misoprostol

Q11. In antidiarrheal screening, inhibition of castor oil-induced diarrhoea is often interpreted as activity against which processes?

• Enteropooling (fluid secretion) and intestinal motility
• Gastric acid hypersecretion only
• Pancreatic enzyme secretion
• Colonic mucosal hypertrophy

Correct Answer: Enteropooling (fluid secretion) and intestinal motility

Q12. Which receptor antagonists are typically evaluated with the apomorphine-induced emesis model to assess efficacy against dopamine-mediated vomiting?

• D2 receptor antagonists (e.g., domperidone)
• H2 receptor antagonists (e.g., ranitidine)
• Beta-2 adrenergic agonists
• Muscarinic M3 receptor agonists

Correct Answer: D2 receptor antagonists (e.g., domperidone)

Q13. A reduction in gastric mucosal prostaglandin E2 level following NSAID administration correlates with which effect relevant to ulcerogenesis?

• Decreased mucosal blood flow and mucus secretion leading to increased susceptibility to ulcers
• Increased gastric emptying improving mucosal defense
• Enhanced bicarbonate secretion protecting mucosa
• Reduced gastric acid production preventing ulceration

Correct Answer: Decreased mucosal blood flow and mucus secretion leading to increased susceptibility to ulcers

Q14. Which of the following is the most appropriate positive control when screening for opioid-type antidiarrheal activity in rodents?

• Loperamide
• Ranitidine
• Ondansetron
• Omeprazole

Correct Answer: Loperamide

Q15. In evaluating potential antiulcer agents, measurement of gastric mucosal hexosamine content is used as an index of what?

• Mucus glycoprotein (mucin) content and mucosal protective barrier
• Systemic inflammation level
• Enteric neuronal density
• Gastric acid neutralization capacity

Correct Answer: Mucus glycoprotein (mucin) content and mucosal protective barrier

Q16. Which experimental endpoint is most appropriate to assess secretory diarrhea induced by cholera toxin in animal models?

• Intestinal fluid accumulation (enteropooling) and cAMP levels in intestinal tissue
• Gastric pH measurement
• Number of vomit episodes
• Colonic transit time assessed by charcoal meal

Correct Answer: Intestinal fluid accumulation (enteropooling) and cAMP levels in intestinal tissue

Q17. When screening stimulatory laxatives (e.g., senna), which histological change in the colon is commonly monitored as a safety parameter?

• Mucosal epithelial hyperplasia/crypt cell proliferation
• Hepatocellular necrosis
• Cardiac myocyte hypertrophy
• Renal tubular dilation

Correct Answer: Mucosal epithelial hyperplasia/crypt cell proliferation

Q18. Which in vivo test would be most appropriate to distinguish between an agent that reduces gastric acid secretion versus one that increases mucosal protection?

• Combined measurement of gastric acid output (e.g., pylorus ligation) and mucin content (Alcian blue)
• Charcoal meal intestinal transit test alone
• Apomorphine-induced emesis test
• Serum electrolyte panel

Correct Answer: Combined measurement of gastric acid output (e.g., pylorus ligation) and mucin content (Alcian blue)

Q19. Ethical considerations in GI screening studies require minimizing animal pain and number used. Which practice aligns with the 3Rs (Replacement, Reduction, Refinement)?

• Using validated in vitro mucus-secreting cell assays to pre-screen compounds before animal testing
• Increasing sample size to detect smaller differences without prior justification
• Using higher-than-necessary doses to ensure an effect
• Skipping analgesia to avoid confounding results

Correct Answer: Using validated in vitro mucus-secreting cell assays to pre-screen compounds before animal testing

Q20. In screening for NK1 receptor antagonists as antiemetics, which physiological mediator’s central action is most relevant to emesis that these antagonists block?

• Substance P acting at NK1 receptors in the brainstem
• Ghrelin release from stomach fundus
• Pancreatic polypeptide secretion
• Bradykinin-mediated peripheral pain signals

Correct Answer: Substance P acting at NK1 receptors in the brainstem

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