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: Physiology
Hot water bottle relieves pain of abdominal spasm by: 
Select and explain. 
A. Stimulation of adrenergic fibers, B. Stimulation of cholinergic fibers, C. Inhibition of cold receptors, D. Inhibition of heat receptors
A: Stimulation of adrenergic fibers
Answer: A: Stimulation of adrenergic fibers 
Explanation: Hot water bottle relieves abdominal pain through stimulation of adrenergically activated A delta and C fibres, there by blocking pain impulses transmitted through visceral C fibers. Ref: The Journey to Pain Relief : A Hands-On Guide to Breakthroughs in Pain Treatment By Phyllis Berger, Page 76; The Neurobiology of Pain : Symposium of the Nohern Neurobiology Group, Page 232; The Human Nervous System : Structure and Function By Charles Robe Noback, Page 171.