Effects of neuronal stimulation on mucosal transport in guinea pig ileum

The effects of electrical stimulation of enteric nerves on mucosal transport parameters were determined in short-circuited flat sheets of guinea pig ileum. Rectangular bipolar stimulus pulses with a duration of 0.5 ms were applied continuously across Ag-AgCl foil electrodes positioned in parallel with the plane of the tissue. Electrical field stimulation (EFS) elicited a biphasic increase in the short-circuit current (Isc) and transmural electrical potential difference. The response to EFS consisted of an initial rapid rise and decline in Isc followed by a slower rise in Isc to a plateau. This response persisted with some decrement. The maximum change in Isc occurred at stimulus strengths of 3.2-5.2 mA and frequencies of 8-10 Hz. The stimulus-evoked increase in Isc was reversibly abolished by 0.1-0.15 microM tetrodotoxin, 22 mM magnesium, and 0.16 mM cadmium. Prior to EFS, net sodium absorption was 2.3 +/- 0.6 mu eq X cm-2 X h-1 in nine animals, and chloride secretion averaged 1.7 +/- 0.8 mu eq X cm-2 X h-1. EFS had no effect on unidirectional or net sodium fluxes or tissue conductance, whereas it increased active chloride secretion from 1.7 +/- 0.8 to 3.9 +/- 0.6 mu eq X cm-2 X h-1. Tetrodotoxin had no effect on resting sodium or chloride fluxes. These results show that EFS evokes an increase in chloride secretion in guinea pig ileum. These results suggest that EFS alters mucosal transport function by activating enteric neurons.