The effect of baclofen (GABAB agonist), diltiazem (muscle relaxant) and placebo will be compared in a double-blinded randomized study for the treatment of NCCP. Cerebral cortical, brainstem and spinal evoked potentials before and after treatment will be evaluated. Results of this study will shed lights on pathogenesis and treatment of NCCP in Chinese.We hypothesize that Baclofen alleviates visceral hyperalgesia in NCCP patients by suppressing afferent sensory pathway.