Toxicology and antidotes: strychnine poisoning: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · Toxicology and antidotes: strychnine poisoning

Sample item

A man who swallowed ground nux vomica seeds has violent generalised extensor spasms triggered by light touch or noise, risus sardonicus and a clear sensorium. Which receptor does the poison block to produce this picture?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Glycine receptors in the spinal cord

Strychnine is a competitive antagonist of the inhibitory neurotransmitter glycine at postsynaptic spinal receptors. Loss of inhibition makes motor neurons hyperexcitable, so minimal stimuli cause tetanus-like spasms while consciousness is preserved. Treatment is a quiet environment with benzodiazepines.

Option by option

  • A. NMDA receptors in the cortex

    NMDA receptor blockade, as with ketamine, causes dissociation rather than spasms.

  • B. Nicotinic receptors at the motor endplate

    Nicotinic receptor blockade causes paralysis and not spasms.

  • C. Glycine receptors in the spinal cord (correct)

    Correct. Strychnine antagonises spinal glycine receptors.

  • D. GABA-A receptors in the brain

    GABA-A receptor blockade, as with picrotoxin, causes seizures with loss of consciousness.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, Glycine receptors in the spinal cord. Strychnine is a competitive antagonist of the inhibitory neurotransmitter glycine at postsynaptic spinal receptors.

Why is "NMDA receptors in the cortex" not the answer?

NMDA receptor blockade, as with ketamine, causes dissociation rather than spasms.

Why is "Nicotinic receptors at the motor endplate" not the answer?

Nicotinic receptor blockade causes paralysis and not spasms.

Why is "GABA-A receptors in the brain" not the answer?

GABA-A receptor blockade, as with picrotoxin, causes seizures with loss of consciousness.

What concept does this question test?

It tests Toxicology and antidotes: strychnine poisoning in Pharmacology. Loss of inhibition makes motor neurons hyperexcitable, so minimal stimuli cause tetanus-like spasms while consciousness is preserved. Treatment is a quiet environment with benzodiazepines.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Toxicology and antidotes: strychnine poisoning?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.