Visceral hypersensitivity as evidence of central sensory sensitization is evident in many patients with functional disorders such as functional dyspepsia (FD) and irritable bowel syndrome (IBS). We recently demonstrated both somatic hypersensitivity and abnormal endogenous pain modulation in IBS, both of which indicate central sensitization as a crucial mechanism in IBS. Endogenous pain mechanisms regulate, fine-tune and integrate sensory and homeostatic, including neuroendocrine, immune, motor and autonomic nervous system processes. Hitherto, no studies have investigated the role endogenous pain modulation in FD. Abnormal modulation could explain several of the symptom complexes associated with FD and provide a rationale for exploration of new treatments.

The current study was designed to

1. investigate the gastric sensitivity in FD patients and healthy controls during gastric capsaicin stimulation
2. assess the endogenous pain inhibitory modulation system in FD patients and healthy controls during heterotopic stimulation

Inclusion Criteria:

FD patients:

• Eighty male and female FD patients according to Rome III criteria (Drossman, 2006), aged 18 to 70 years, will be recruited from primary and secondary care via advertisements and our referral networks.
• FD discomfort or pain should be the most prominent symptom.
• Patients must have been off all FD and analgesic medication and any drugs potentially influencing sensory function for at least two weeks before study start and be able to remain off such medication for the duration of the study period.

Healthy controls:

• Forty male and female healthy volunteers, aged 18 to 70 years without any gastrointestinal pathology or history of significant abdominal pain, bowel disorders, bloating or discomfort during the last 3 months will be recruited.

Exclusion Criteria:

Exclusion criteria for both FD patients and healthy controls:

• Organic gastrointestinal or other significant systemic disease, including cardiovascular, dermatological, psychiatric, neurological and endocrine diseases. Patients with peptic ulcer scars are also excluded.
• Chronic or acute pain, except related to other functional syndromes (irritable bowel syndrome, chronic pelvic pain, fibromyalgia, migraine).
• H. pylori positive.
• Abdominal surgery, including gastric resection or cholecystectomy (except appendectomy)
• History of brain disease or brain surgery.
• Ongoing treatment with any drugs or need for drugs (or complementary medication) within last 14 days.
• Treatment with any investigational drug during the preceding 30 days.
• Ingestion of spicy, chilli pepper containing meal, or use of capsaicin skin cream in last 48 hours before start of study or any study day.
• Pregnancy or lactation.
• No written informed consent obtained from subject.