The effects of fasting on neuronal NO synthase (nNOS), Heme oxygenase 2 (HO-2), and heat shock protein 90 (HSP90) was determined by immunoblotting in the stomach, duodenum, mid-jejunum, distal ileum, and proximal colon of 28-day-old piglets. nNOS expression was drastically reduced in all the gastrointestinal areas studied while HO-2 was not changed. Concomitant with the nNOS decrease, elevated expressions of HSP90 were observed in these different areas. These results are discussed in terms of the regulation relationship between NOS and HSP90 and the possible protective effect of the heat shock protein and the potential application in digestive pathologies.