Role of the enteric nervous system in piglet cryptosporidiosis

Piglet cryptosporidiosis is characterized by intestinal villous damage and malabsorption and by reduced NaCl absorption in response to prostaglandin (PG) release from inflamed tissue. We hypothesized that the PG effect is mediated by the enteric nervous system. Piglets were infected with cryptosporidium and ileal mucosa was studied in Ussing chambers. Studies with tetrodotoxin and indomethacin showed that 75% of the PG-induced alteration in NaCl transport was mediated by the enteric nervous system. Prostacyclin was elevated in infected tissue, and its analog, carbacyclin, mimicked the altered transport response in indomethacin-treated tissue. This carbacyclin response was abolished by tetrodotoxin. The vasoactive intestinal peptide (VIP) receptor antagonist, VIP-10-28, and the muscarinic antagonist, atropine, individually reduced and together abolished the response to carbacyclin, whereas the nicotinic blocker, hexamethonium, reduced the carbacyclin response by 75%. The somatostatin analog, octreotide, and the a-2 adrenergic agonist, clonidine, each abolished the carbacyclin response and partially or completely rectified the altered NaCl transport of the infection. These results indicate that PGs alter NaCl transport in this infection primarily by stimulating cholinergic interneurons that innervate VIPergic and cholinergic motor nerves. The enteric nervous system may be a potential target for pharmacological control of the acute diarrhea in this infection.