Distribution of peptide transporter PEPT2 mRNA in the rat nervous system

The signaling action of neuropeptides in the is terminated by breakdown thr ough extracellular peptidases and subsequent removal of the peptide fragmen ts from the extracellular fluid via specific transporter proteins. Here we describe the anatomical distribution in the rat nervous system of the recen tly isolated high affinity peptide transporter PEPT2. Using nonisotopic in situ hybridization we demonstrate that PEPT2 mRNA is expressed in brain by astrocyte, subependymal cells, ependymal cells and epithelial cells of chor oid plexus. Furthermore, PEPT2 is expressed in retina by Muller cells and i n dorsal root ganglia by satellite cells. The mRNA levels of PEPT2 in astro cytes are moderate and relatively homogenous throughout the brain except fo r an area in ventral forebrain where PEPT2 levels are below average. PEPT2 mRNA expression is weakly upregulated in reactive astrocytes that were stim ulated through an injection of the glutamatergic neurotoxin quinolinic acid . These data suggest that removal of neuropeptide fragments from brain extr acellular fluid occurs via PEPT2 expressed in astrocytes, ependymal cells a nd choroid plexus epithelial cells.