Hot water bottle relieves the pain of abdominal spasm by: (A) Stimulation of adrenergic fibers, (B) Stimulation of cholinergic fibers, (C) Inhibition of cold receptors, (D) Inhibition of heat receptors
Answer is A. Pain from gastrointestinal viscera is carried by small C fibers. Temperature sensation from hot water bottles passes through A fibers and large C fibers. 
When these larger fibers are stimulated, they block the adrenergic small C fibers from the viscera.