Neural regulation of duodenal alkali secretion: effects of electrical field stimulation

The role of transmitters released from enteric neurons in regulating bicarbonate secretion by the proximal duodenum has been studied using electrical field stimulation (EFS). Stripped duodenal mucosa from Rana catesbeiana was mounted as an intact tube over circular platinum electrodes, and luminal alkalinization was measured by pH stat titration before, during, and after EFS. Transmucosal potential difference (PD) was simultaneously measured before and after EFS by paired electrodes. Square-wave pulses 50 V, 2 ms in duration, at 10 Hz were delivered in trains of 0.5 s at 1 Hz for periods of 15 min after stable basal secretion. This resulted in a 63 +/- 27% increase in alkalinization that returned to basal values after cessation of the stimulus, without change in transmucosal PD. Serosal-to-lumen [3H]mannitol flux was not affected. Repetition of the stimulus resulted in similar responses for as long as the tissue remained viable. The response to EFS was abolished by tetrodotoxin (10(-6) M) and veratrine (0.1 mg/ml), indicating that intrinsic neurons were responsible for mediating the effect. In addition, the effect was blocked by serosal dinitrophenol (10(-4) M), indicating that the secretory response occurred by a metabolically dependent process. These results indicate that alkalinization by proximal duodenum may be controlled by neurotransmitter release from local enteric neurons.