Drewes_2005_J.Pain_6_455

It is believed that mechanical stimuli of the human gut activate afferents responding to either noxious or normal, physiologic stimuli. They might be able to sensitize without relation to the contractile state of the smooth muscle. The current study aimed to verify the above characteristics by using a statistical model based on correlation analysis. The esophagus was distended with a bag in 32 healthy subjects by using an inflation rate of 25 mL/min. The luminal cross-sectional areas and sensory ratings were determined during the distentions. The stimuli were repeated after relaxation of the smooth muscle with butylscopolamine and after sensitization with hydrochloride acid. A positive correlation between the sensory responses to distention was found in the non-painful and painful ranges, respectively, but correlations between non-painful and painful ratings were nonsignificant. Relaxation of the smooth muscle did not influence the correlations, and sensitization resulted in inter-individual differences and disappearance of the above clustering into painful and non-painful correlations. In conclusion, afferent nerves encoding high-threshold and low-threshold mechanical stimuli of the human esophagus are not correlated and thus probably represent different populations. The response characteristics have no physiologic relationship to the contractile state of the smooth muscle, and sensitization affects all types of afferents. PERSPECTIVES: The article adds information about sensory processing of mechanical gut stimuli in human beings. This might increase our understanding of visceral pain in health and disease and guide the statistical analysis of experimental data obtained in the gastrointestinal tract.