This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
[{'content': '52 yrs male presented with muscular stiffness and painful cramps.The face was drawn into a forced grimace (“sardonic grin,” or risus sardonicus). Strychnine Poisoning was suspected; Strychnine is supposed to antagonizes competitively: - \nSelect and explain. \nA. Glycine, B. Glutamate, C. Succinyl choline, D. Acetyl choline', 'role': 'user'}, {'content': 'Answer: A \nExplanation: STRYCHNINE POISONING\nMechanism of toxicity.\nStrychnine competitively antagonizes glycine, an inhibitory neurotransmitter released by post-synaptic inhibitory neurons in the spinal cord. Clinical presentation.\nMuscular stiffness and painful cramps precede generalized muscle contractions and opisthotonos.\nThe face may be drawn into a forced grimace (“sardonic grin,” or risus sardonicus).\nRepeated and prolonged muscle contractions often result in hyperthermia, rhabdomyolysis, myoglobinuria, and renal failure.\nHyperacusis, hyperalgesia, and increased visual stimulation.\nDeath is usually caused by respiratory arrest owing to intense contraction of the respiratory muscles.', 'role': 'assistant'}]