Expression of the neuropeptide Y Y1 receptor mRNA in the human brain

Using cRNA in situ hybridization, the regional distribution of mRNA encoding the human Y1 receptor was investigated in the normal human brain and compared with the autoradiographic distribution of putative Y1/[125I][Leu31,Pro34]PYY binding sites. Surprisingly, relatively high levels of Y1 receptor mRNA, distributed in a ty laminar fashion, were detected in the frontal and temporal cortices; laminae I, IV and VI were particularly enriched. The claustrum and nucleus of the medial geniculate body also revealed high levels of Y1 receptor mRNA signals. Moderate levels of specific hybridization were detected in the caudate nucleus, putamen, nucleus accumbens, amygdaloid nuclei, and arcuate and paraventricular nuclei of the hypothalamus. In all these regions, only very low levels of specific [125I][Leu31,Pro34]PYY binding were detected with the exception of the dentate gyrus of the hippocampal formation which expressed rather high levels of both the Y1 receptor mRNA and its translated protein. Accordingly, the human brain can express the Y1 receptor mRNA but this may not necessarily translate into a functional receptor as revealed by low specific binding levels observed in most regions.