The following has a selective morphine like effect on G.I.T.:

Correct Answer: A

Rationale: Loperamide (choice A), a mu-opioid agonist, acts peripherally on GIT receptors, reducing motility and treating diarrhea without significant CNS effects due to poor blood-brain barrier penetration. Pentazocine (choice B), a mixed agonist-antagonist, and Heroin (choice C), a full agonist, primarily affect the CNS, not selectively the GIT. Neostigmine (choice D), a cholinesterase inhibitor, increases motility, opposing morphine's effect. Loperamide's selective GIT action makes it ideal for diarrhea, distinguishing it from systemic opioids.

Correct Answer: B

Rationale: Benzodiazepines reduce anxiety (choice A), control seizures (choice C), and relax muscles (choice D) via GABAa enhancement. They lack antipsychotic action (choice B), which requires dopamine D2 blockade (e.g., haloperidol), not GABA modulation. This exception differentiates anxiolytics from antipsychotics in CNS therapy.

Correct Answer: B

Rationale: Chlorpromazine, a typical antipsychotic, blocks D2 receptors (choice B) in the mesolimbic pathway, reducing positive schizophrenia symptoms. D1 blockade (choice A) is less critical, adrenergic (choice C) and opiate (choice D) blockade are side effects, not primary. D2 antagonism is its core mechanism.

Correct Answer: A

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: D

Rationale: Thiopentone (choice A), Isoflurane (choice B), and Procaine (choice C) match their indications (anesthesia induction, maintenance, local anesthesia). Chlorpromazine (choice D), an antipsychotic, causes hypotension as a side effect, not a treatment, making it false. This tests drug-indication accuracy.