Electrically evoked cerebral potentials during esophageal distension at perception and pain threshold

To investigate esophageal sensory function in normal volunteers.

The method of evoking cerebral potentials (EPs) after electrical stimulation of the esophagus was applied in eight healthy male volunteers, 20-40 yr old. Electrical stimulation was obtained via bipolar Ag/AgCl electrodes attached to a latex balloon mounted on a catheter. The balloon was inflated stepwise to perception and pain thresholds. At the perception threshold for balloon distension, the intensity of electrical stimulation was increased stepwise to perception threshold for electrical stimulation, and subsequently to 2-fold, 4-fold, and 8-fold perception threshold. EPs were recorded from the vertex (Cz) and forehead (Fz, reference) and compared between the increasing electrical stimulation intensities and between perception and pain thresholds for mechanical stimulation.

The results show that amplitudes of EPs significantly increased with increasing electrical stimulation intensities, whereas latencies of EPs were not affected. Latencies and amplitudes of EPs were comparable at perception and pain thresholds for esophageal distension.

The study suggests that repetitive electrical stimulation of the human esophagus is predominantly mediated via vagal A-delta fibers. The unaltered EPs at the perception and pain thresholds suggest that vagal A-delta fibers are not involved in mediation of pain. The findings support the view that painful and nonpainful stimuli are mediated via different visceral afferents between the esophagus and brain in humans.