Match List-I with List-II List-I (Class): (A). Reflex acting... | Agrigyan

Receptor ion-channel physiology:

• Nicotinic acetylcholine receptor ($N_m$): Ligand-gated cation channel allowing predominantly $\text{Na}^+$ influx into skeletal muscle -> (A) is correct.
• Glycine receptor: Ligand-gated anion channel in the spinal cord allowing $\text{Cl}^-$ influx, causing inhibitory hyperpolarization -> (B) is correct.
• $\text{GABA}_A$ receptor: Ligand-gated ionotropic chloride channel allowing $\text{Cl}^-$ influx -> (C) is correct.
• $\text{GABA}_B$ receptor: G-protein coupled metabotropic receptor, not a ligand-gated chloride channel (it activates $\text{K}^+$ efflux and inhibits $\text{Ca}^{2+}$ channels) -> (D) is incorrect.
  
  Option analysis:
  Statements (A), (B), and (C) are correct, while (D) is false. Thus, Option 2 is correct.

Pharmacological receptor targets of gastrointestinal drugs:

• Ranitidine: Competitive histamine $H_2$ receptor antagonist -> (A) matches (III).
• Ondansetron: Selective serotonin $5\text{-HT}_3$ receptor antagonist used as antiemetic -> (B) matches (IV).
• Metoclopramide: Dopamine $D_2$ receptor antagonist with prokinetic and central antiemetic action -> (C) matches (I).
• Pirenzepine: Selective muscarinic $M_1$ receptor antagonist suppressing gastric acid secretion -> (D) matches (II).
  
  Option analysis:
• Ranitidine -> (III).
• Ondansetron -> (IV).
• Metoclopramide -> (I).
• Pirenzepine -> (II). Matches Option 3.

Classification of laxatives and purgatives:

• Lactulose: Synthetic non-absorbable disaccharide that draws water into the gut lumen via osmosis (Osmotic purgative) -> (A) is correct.
• Bisacodyl: Diphenylmethane derivative that stimulates enteric mucosal nerve endings to promote peristalsis (Stimulant/irritant purgative) -> (B) is correct.
• Poloxamer: Non-ionic surfactant used as a stool softener / fecal wetting agent (detergent/emollient laxative), not a bulk purgative -> (C) is incorrect.
• Ispaghula (Psyllium husk): Rich in mucilage that absorbs water, expands, and adds mechanical bulk to feces (Bulk purgative) -> (D) is correct.
  
  Option analysis:
  Statements (A), (B), and (D) are correctly classified, making Option 1 the correct answer.