A high concentration of NPY (Y1)-receptor mRNA-expressing cells in the rat arcuate nucleus

The Y1 neuropeptide Y (NPY) receptor cDNA was recently cloned from a rat brain library. In situ hybridization histochemistry using a synthetic oligonucleotide probe complimentary to bases 716-764 of the Y1 receptor cDNA was used to localize the corresponding mRNA in the rat brain with special reference to the hypothalamic arcuate-paraventricular axis, because these areas are considered to play a key role in eating behavior. Quantification of the hybridization signals by a computerized image analyzing system revealed that the arcuate nucleus together with the granular cell layer in the gyrus dentatus contained a high concentration of Y1 mRNA. In emulsion-dipped sections, the neurons containing Y1 mRNA transcripts were found particularly in the ventromedial part of the arcuate nucleus. These data indicate that NPY or NPY-related peptides via a Y1 receptor on neurons of the arcuate nucleus may influence the homeostasis.