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: Pharmacology
All adverse effects of theophylline are mediated by A1, receptor except: 
Select and explain. 
A. Cardiac arrhythmias, B. Dieresis, C. Seizures, D. GI discomfo
D: GI discomfo
Answer: D: GI discomfo 
Explanation: Theophylline exes it's bronchodilation effect by PDE inhibition effect and Adenosine A1 antagonism. It has multiple side effect : Nausea and vomiting PDE inhibition Headache PDE inhibition Gastric discomfo PDE inhibition Diuresis Adenosine A1 antagonism Arrythmias PDE inhibition, A 1 antagonism Seizures Adenosine A1 antagonism