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

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Abstract
Whether transmitters released from enteric neurons can elicit secretion from goblet cels was studied using full-thickness sheets of adult rat distal ileum of descending colon mounted in modified Ussing chambers. 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 .mu.M tetrodotoxin (TTX) or 10 .mu.M 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 .mu.M carbachol. Thus, intrinsic cholinergic neurons may be stimulated during the mounting of the ileum in the chamber. 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.