The calcium-binding protein neuronal calcium sensor 1 (NCS-1) is involved in modulation of neurotransmitter release in the peripheral and central nervous systems. Since intestinal inflammation impairs neurotransmitter release, we evaluated the expression of NCS-1 in the normal rat colon and in dinitrobenzene sulfonic acid (DNBS)-induced colitis. Immunocytochemistry and Western blots showed high levels of NCS-1 in the myenteric plexus and in axons in the smooth muscle layers; 23 ± 2% of myenteric neurons were NCS-1 positive, with staining restricted to the largest neurons. NCS-1-positive axons decreased to 13.3 ± 0.4% of total axons by day 2 and dropped further to 7.0 ± 0.1% by day 4, returning to control levels by day 16. Dual-label Western blot analysis showed that the expression of NCS-1 relative to PGP 9.5 decreased by 50% onday 4 but returned to control by day 16. The selective loss of NCS-1 during colitis may underlie the altered neural function seen in the inflamed intestine.