ESOPHAGEAL SENSATION ASSESSED BY ELECTRICAL STIMULI AND BRAIN EVOKED-POTENTIALS - A NEW MODEL FOR VISCERAL NOCICEPTION

Sensory thresholds and brain evoked potentials were determined in 12 h ealthy volunteers using electrical stimulation of the oesophagus 28 an d 38 cm from the nares. The peaks of the evoked potentials were design ated N for negative deflections and P for positive. Continuous electri cal stimulation (40 Hz) at the 38 cm position resembled heartburn (fiv e of 12 subjects) while non-specific ('electrical') sensations were pr ovoked at 28 cm (10 of 12). Thresholds of sensation and of pain were l ower at the initial than the second determination, but did not differ with respect to stimulation site. The pain summation threshold to repe ated stimuli (2 Hz, 5 stimuli) was determined for the first time in a viscus. This threshold was lower than the pain threshold to single sti muli at 38 cm (p < 0.02). Evoked potential latencies did not change si gnificantly over a six month period while the N1/P2 amplitude was high er at the first measurement (p < 0.05). P1 and N1 latencies were signi ficantly shorter 38 cm (medians 100 and 141 ms) than 28 cm from the na res (102 and 148 ms) (p = 0.04 and p = 0.008). Electrical stimulation of the oesophagus may serve as a human experimental model for visceral pain. Longer evoked potential latencies from the proximal compared wi th distal stimulations provide new information about the sensory pathw ays of the oesophagus.