Regulation of intestinal goblet cell secretion. IV. Electrical field stimulation in vitro

To determine whether transmitters released from enteric neurons can elicit secretion from goblet cells, full-thickness sheets of adult rat distal ileum or descending colon were mounted in modified Ussing chambers, and mucus secretion was assessed morphologically after electrical field stimulation (EFS). Square-wave pulses (56 V, 2 ms duration) were delivered at 10 Hz for 5 min. Goblet cells in colonic crypts, but not those on the mucosal surface, secreted mucus in response to EFS. This secretion was at least in part atropine insensitive, indicating a noncholinergic mechanism. In the ileum goblet cells located in the crypts, but not on villi, secreted mucus when tissue was mounted in the chamber, even in the absence of EFS. This "unelicited" secretion did not occur in unmounted control tissue in vitro, and it could be prevented by preincubating ileal tissue in 1 microM tetrodotoxin (TTX) or 10 microM atropine for 15 min before mounting. Furthermore, following preincubation with either TTX or atropine, EFS' failed to elicit secretion. Incubation of unmounted tissue with TTX, however, did not block the secretory response of crypt goblet cells to 20 microM carbachol. Thus, intrinsic cholinergic neurons may be stimulated during the mounting of the ileum in the chamber. Taken together, these data demonstrate that mucus secretion from crypt goblet cells may be regulated by cholinergic (in ileum and perhaps colon) and noncholinergic (in colon) elements of the enteric nervous system.