Influence of GABA-B Agonist Baclofen on Capsaicin-Induced Excitation of Secondary Peristalsis in Humans.

OBJECTIVES

Esophageal instillation of capsaicin enhances secondary peristalsis, but the γ-aminobutyric acid receptor type B (GABA-B) agonist baclofen inhibits secondary peristalsis. This study aimed to investigate whether baclofen could influence heartburn perception and secondary peristalsis subsequent to capsaicin infusion in healthy adults.

METHODS

Secondary peristalsis was performed by slow and rapid mid-esophagus air injections in 15 healthy subjects. Two different sessions including esophageal infusion of capsaicin-containing red pepper sauce (0.84 mg) following pre-treatment with placebo or baclofen were randomly performed to test the effects on heartburn perception and secondary peristalsis.

RESULTS

The intensity of heartburn symptom subsequent to capsaicin infusion was significantly greater after pre-treatment of baclofen as compared with the placebo (P=0.03). Baclofen significantly increased the threshold volume of secondary peristalsis to slow air injections subsequent to esophageal capsaicin infusion (P<0.001). Baclofen significantly increased the threshold volume of secondary peristalsis to rapid air injections subsequent to esophageal capsaicin infusion (P<0.01). The frequency of secondary peristalsis subsequent to capsaicin infusion was significantly decreased with baclofen as compared with the placebo (P<0.002). Baclofen had no effect on any of the peristaltic parameters of secondary peristalsis subsequent to capsaicin infusion.

CONCLUSIONS

The GABA-B agonist baclofen appears to attenuate the esophagus to capsaicin-induced excitation of secondary peristalsis in healthy adults. Our study suggests the inhibitory modulation for GABA-B receptors on capsaicin-sensitive afferents mediating secondary peristalsis in human esophagus.