Expression of Secretin in Porcine and Rat Central Nervous System

Abstract

Many intestinal hormones are also distributed throughout the central nervous system (CNS). However, the existence of secretin, a typical intestinal hormone, has not been clearly shown in the brain. There have been conflicting data concerning the expression of secretin in the CNS. The aim of this study was to confirm the existence of secretin in the CNS immunochemically and histochemically. Proforms of secretin were detected in porcine cortex extracts by gel filtration chromatography and reverse-phase HPLC with a radioimmunoassay using different specific antibodies raised against secretin and prosecretin (1-41), indicating the production and processing of secretin precursor in the CNS. An immunocytochemical search in several regions of the rat CNS with the two antibodies revealed that secretin-positive neurons were concentrated in a limited area ranging from the corner of the dentate gyrus to the molecular layer in the hippocampus. In situ hybridization also supported this finding. The limited location of secretin-positive cells shown here caused difficulty in detecting secretin in the CNS. The hippocampus is thought to contribute to aging, and secretinergic neurons in this region might play an important role. This study suggests that secretin is produced in the CNS and may act as a neurotransmitter or neuromodulator in the hippocampus.