Descending Inhibitory Pain Modulation Is Impaired in Patients With Chronic Pancreatitis  Søren Schou Olesen, Christina Brock, Anne Lund Krarup, Peter Funch–Jensen, Lars Arendt–Nielsen, Oliver H. Wilder–Smith, Asbjørn Mohr Drewes  Clinical Gastroenterology and Hepatology  Volume 8, Issue 8, Pages 724-730 (August 2010) DOI: 10.1016/j.cgh.2010.03.005 Copyright © 2010 AGA Institute Terms and Conditions

Figure 1 The protocol used for the experiment. The cold pressor test was used as conditioning stimulus to induce descending pain inhibition (DNIC) in healthy volunteers and patients with chronic pancreatitis. Somatic pressure stimulations of the quadriceps muscle were used to quantify the effect of DNIC. To investigate central pain processing, multimodal (electrical, heat, and mechanical) stimulation of the rectosigmoid was performed. Simultaneous recordings of evoked brain potentials were obtained during the electrical stimulations of the rectosigmoid. Median nerve stimulations with simultaneous recordings of evoked brain potentials were performed to evaluate the presence of neuropathy in peripheral or central nervous pathways. ep, evoked brain potential. Clinical Gastroenterology and Hepatology 2010 8, 724-730DOI: (10.1016/j.cgh.2010.03.005) Copyright © 2010 AGA Institute Terms and Conditions

Figure 2 Tolerance thresholds to somatic pressure stimulation of the quadriceps muscle before and after experimental induction of DNIC in healthy volunteers (dotted line) and in patients with CP (solid line). Patients showed less increase in the tolerance thresholds as compared with healthy volunteers (F = 3.8; P = .01). This finding also was valid in a subanalysis of the opioid-naive patients (F = 3.2; P = .03). (A) The whole patient group (n = 25) versus healthy volunteers (n = 15). (B) The opioid-naive patient group (n = 10) versus healthy volunteers (n = 15). Clinical Gastroenterology and Hepatology 2010 8, 724-730DOI: (10.1016/j.cgh.2010.03.005) Copyright © 2010 AGA Institute Terms and Conditions

Figure 3 Thresholds to electrical stimulations of the rectosigmoid in healthy volunteers (white) and patients with CP (grey). Error bars indicate the standard error of the mean. Patients were hypersensitive to electrical stimulations (F = 6.2; P = .02). Clinical Gastroenterology and Hepatology 2010 8, 724-730DOI: (10.1016/j.cgh.2010.03.005) Copyright © 2010 AGA Institute Terms and Conditions

Figure 4 Thresholds to heat stimulations of the rectosigmoid colon in healthy volunteers (white) and patients with CP (grey). Error bars indicate the standard error of the mean. Patients were hypersensitive to heat stimulations (F = 5.9; P= .02). Clinical Gastroenterology and Hepatology 2010 8, 724-730DOI: (10.1016/j.cgh.2010.03.005) Copyright © 2010 AGA Institute Terms and Conditions

Figure 5 Latencies and peak-to-peak amplitudes of evoked brain potentials obtained after electrical stimulation of the rectosigmoid in healthy volunteers (white) and patients with CP (grey). The 4 earliest components (N1–P2) of the evoked potentials are shown. Error bars indicate the standard error or the mean. *P = .02. Clinical Gastroenterology and Hepatology 2010 8, 724-730DOI: (10.1016/j.cgh.2010.03.005) Copyright © 2010 AGA Institute Terms and Conditions