A man found unconscious after consuming rat poison develops recurrent generalized convulsions with opisthotonus, risus sardonicus, and full consciousness between fits. The toxin acts by:
- A Antagonizing GABA at the brainstem reticular formation
- B Causing sustained depolarization at the neuromuscular junction
- C Antagonizing inhibitory glycine at spinal cord and brainstem interneurons ✓
- D Blocking presynaptic release of acetylcholine
Correct answer: C. Antagonizing inhibitory glycine at spinal cord and brainstem interneurons
Explanation
Strychnine competitively blocks the inhibitory neurotransmitter glycine at postsynaptic receptors on spinal cord and brainstem motor neurons, removing reciprocal inhibition and producing reflex spasms triggered by minimal stimuli. Consciousness is retained between convulsions, which distinguishes it from most other convulsant poisons. Presynaptic acetylcholine blockade describes botulinum toxin, and GABA antagonism at higher centres better fits picrotoxin.
Reference: Parikh's Textbook of Medical Jurisprudence, Forensic Medicine and Toxicology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.