This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
. Respiratory centre depression is caused by all except- 
Select and explain. 
A. Opium, B. Strychnine, C. Barbiturates, D. Gelsemium
B: Strychnine
Answer: B: Strychnine 
Explanation: Strychnine is a toxic alkaloid that acts as an antagonist of the inhibitory glycine receptor of CNS,thereby producing overstimulation of nervous system. Barbiturates,opioids and gelsemium(yellow jasmine) are potential respiratory centre depressants.