Neuromodulation of ion transport in porcine distal colon: NPY reduces secretory actions of leukotrienes.

Electrical transmural stimulation (ETS) was used to examine the neuroregulation of electrolyte transport in the porcine distal colon. ETS of the colonic mucosa-submucosa mounted in Ussing chambers produced rapid and transient increases in short-circuit current (Isc) that were inhibited 36% by serosal bumetanide, suggesting that a portion of the response may be attributed to Cl secretion. ETS actions were dependent upon stimulus intensity and frequency and were inhibited by tetrodotoxin and omega-conotoxin. Prazosin and pyrilamine had no effect on the mucosal responses to ETS, whereas atropine reduced the responses by 32%. Neuropeptide Y (NPY) also reduced the mucosal responses to ETS up to 60% (half-maximal effective concentration = 17 nM). In addition, the effects of leukotriene C4, previously shown to stimulate Cl secretion via a neuronal pathway, were also inhibited by NPY. These results indicate that cholinergic submucosal neurons play a role in the regulation of epithelial ion transport and that NPY acts as an inhibitory neuromodulator, particularly on leukotriene-sensitive neurons in the porcine distal colon.