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.