The mechanism of action of bombesin on cat lower esophageal sphincter.

The effect of bombesin on the tone and the responses of strips from the lower esophageal sphincter (LES) to field electrical stimulation (FES) (2 Hz, 0.2 ms, supramaximal current intensity, 20 s duration) was studied. Bombesin dose-dependently increased the LES tone. The threshold for this effect was 10(-14) M and was particularly pronounced with a concentration of 10(-8) M. The response reached maximum between the 3rd and the 5th min after application, persisted for 15-20 min, and was followed by a slight time-dependent decrease. Bombesin increased FES-produced relaxation of LES by 39% as compared to the control. The potentiating effect of bombesin on the LES relaxation was also observed after cholinergic and adrenergic receptor blockade. It is concluded that bombesin may modulate the release of cholinergic, adrenergic and noncholinergic, nonadrenergic inhibitory neurotransmitters.