Vasoactive intestinal polypeptide (VIP) has been postulated as a
neuropeptide with inhibitory
neurotransmitter activity in nonadrenergic noncholinergic pathways.
Transcutaneous electric nerve stimulation (
TENS) relaxes the lower esophageal sphincter in patients with
achalasia. Such response is accompanied by a 30% increase in VIP concentrations in the systemic circulation. Since the sphincter of Oddi (SO) receives a very dense VIP nerve supply, we evaluate the effect of
TENS on SO motor activity and on VIP plasma concentrations in patients with
biliary dyskinesia and in healthy volunteers.
TENS was performed with a pocket stimulator for 45 min. SO pressure and VIP levels were obtained before and after 45 min of
TENS. In patients with SO
dyskinesia,
TENS produced a significant decrease in SO pressure from 80.1 +/- 11.9 mm Hg to 58.3 +/- 9.7 mm Hg p less than 0.01); this was accompanied by a significant increase in VIP plasma levels from 21.1 +/- 0.5 pg/ml to 32.6 +/- 1.5 pg/ml (p less than 0.01). In healthy volunteers,
TENS did not produce significant changes in SO pressure. However, a significant increase in VIP plasma values was observed (p less than 0.01). No significant changes in amplitude, duration and frequency of SO phasic contractions were observed in either of the two groups evaluated. We conclude that, in patients with SO
dyskinesia,
TENS decreases SO basal pressure, possibly by a direct action of the released VIP in the systemic circulation. In healthy volunteers,
TENS increases VIP plasma values without significant effect on SO basal pressure. These findings suggest that the response to
TENS may be mediated by VIP. It is also possible that the alterations seen in patients with
biliary dyskinesia may be due to impairment of the VIP nerve supply at the level of the SO.