NEURALLY MAINTAINED HYPERSECRETION IN UNDERNOURISHED RAT INTESTINE ACTIVATED BY ESCHERICHIA-COLI STA ENTEROTOXIN AND CYCLIC-NUCLEOTIDES IN-VITRO

1. The electrogenic secretory responses of stripped jejuna and ilea fr om chronically undernourished rats (50% control diet for 21 days) to t he bacterial enterotoxin Escherichia coli STa, measured as the short-c ircuit current in vitro, show an enhanced maximum secretion (I-sc,I-ma x) with a prolonged duration compared with fed intestine. 2. The I-sc, I-max is unaffected by pretreatment of the intestine in vitro with hex amethonium, atropine, procaine or indomethacin, or by desensitization to 5-hydroxytryptamine (5-HT), while the prolonged duration is unaffec ted by atropine, indomethacin or 5-HT desensitization but is reduced b y hexamethonium and procaine. 3. Both 8-bromo-cyclic GMP and dibutyryl cyclic AMP added serosally activate the enhanced I-sc,I-max and its m aintenance. Pretreatment with tetrodotoxin had no effect on the initia l I-sc,I-max but prevented its maintenance. 4. Bethanechol, dimethyl p henyl piperazinium, vasoactive intestinal polypeptide, 5-HT and lumina l propionate all induced the characteristic hypersecretory activity in the undernourished intestine compared with the fed state, but none co uld activate the maintenance circuit to prolong their transient respon ses. 5. Maintenance of the induced hypersecretory activity is the firs t example of induction of the neural control of intestinal secretion b y the dietary intake level and illustrates the plasticity of the enter ic nervous system.