Expression of the gene encoding neurotensin (NT/N) is developmentally regulated in the adult small bowel with maximal expression noted in the distal ileum; the mechanisms responsible for this strict spatial-specific expression pattern are not known. The purpose of this study was to determine whether NT/N expression is altered by ileojejunal transposition. Rats underwent either sham operation or ileojejunal transposition and were killed 2 months after operation. The transposed (either jejunum or ileum) and sham-operated segments of gut were removed, a portion was processed for histologic examination, and the remainder was extracted for total RNA and analyzed by ribonuclease protection using a rat NT/N probe. For comparison, expression of another gut endocrine gene, peptide YY, and an enterocyte-specific gene, sucrase-isomaltase (SI), was also determined. Expression of the gut endocrine genes, NT/N and peptide YY, were minimally affected by transposition of either the jejunum or ileum. In contrast, SI expression was markedly altered in both the transposed jejunum and ileum compared with corresponding sham gut segments. Expression of the NT/N gene is minimally altered after jejunoileal transposition despite marked adaptive and morphologic changes in the transposed segments. These findings provide further support that the strict pattern of NT/N expression is "imprinted" in the gut and maintained regardless of location along the cephalocaudal gut axis.