Neurally maintained hypersecretion in undernourished rat intestine activated by E. coli STa enterotoxin and cyclic nucleotides in vitro.

1. The electrogenic secretory responses of stripped jejuna and ilea from chronically undernourished rats (50% control diet for 21 days) to the bacterial enterotoxin Escherichia coli STa, measured as the short-circuit current in vitro, show an enhanced maximum secretion (ISC, max) with a prolonged duration compared with fed intestine. 2. The ISC, max is unaffected by pretreatment of the intestine in vitro with hexamethonium, atropine, procaine or indomethacin, or by desensitization to 5-hydroxytryptamine (5-HT), while the prolonged duration is unaffected by atropine, indomethacin or 5-HT desensitization but is reduced by hexamethonium and procaine. 3. Both 8-bromo-cyclic GMP and dibutyryl cyclic AMP added serosally activate the enhanced ISC, max and its maintenance. Pretreatment with tetrodotoxin had no effect on the initial ISC, max but prevented its maintenance. 4. Bethanechol, dimethyl phenyl piperazinium, vasoactive intestinal polypeptide, 5-HT and luminal propionate all induced the characteristic hypersecretory activity in the undernourished intestine compared with the fed state, but none could activate the maintenance circuit to prolong their transient responses. 5. Maintenance of the induced hypersecretory activity is the first example of induction of the neural control of intestinal secretion by the dietary intake level and illustrates the plasticity of the enteric nervous system.