Site and mechanism of pain perception with oesophageal balloon distension and intravenous edrophonium in patients with oesophageal chest pain.

Ten healthy volunteers and 13 patients with oesophageal motility disorders whose primary presenting complaint was chest pain were studied by distending an intraoesophageal balloon in 1 ml steps to the point of a sensation of discomfort. The net balloon pressure (intra-balloon pressure when inflated within the oesophagus minus the pressure recorded at the same volume outside the patient) was measured at each volume increment and the distension volume at the perception of discomfort was noted. The measurements were repeated after intravenous injection of edrophonium (80 micrograms/kg) and again after 1.2 mg intravenous atropine. Oesophageal wall compliance was similar in patients and controls, and the two groups showed a similar effect of decreased compliance with edrophonium and increased compliance after atropine. There were no significant differences between patients and controls of distending volume at perception of discomfort. Edrophonium, however, resulted in a significant reduction in distension threshold for pain (p less than 0.03) in patients. A similar though non-significant trend was seen in controls. In both controls and patients, distension volume for pain production after atropine was significantly (p less than 0.01) higher than after edrophonium. From these results and other published data, we suggest that the pain receptor for noxious stretch and after edrophonium challenge is likely to be an 'in series' mechanoreceptor located in oesophageal longitudinal muscle.