Differential expression of neurotensin receptor mRNA in the dopaminergic cell groups of the rat diencephalon and mesencephalon

Abstract

Several lines of evidence support interactions between neurotensin (NT) and dopaminergic (DAergic) neurons in the brain. In order to obtain further knowledge about the anatomical substrate for such interactions, the distribution of cells expressing the cloned neurotensin receptor (NTR) mRNA was examined in relation to tyrosine hydroxylase (TH) mRNA-expressing cells within different subnuclei of the diencephalon and ventral mesencephalon of the male rat. In situ hybridization was performed on consecutive sections labeled with 33P-labeled oligonucleotide probes. In the hypothalamus, NTR mRNA signals were mostly found in the suprachiasmatic, dorsomedial, dorsal premammillary, and supramammillary nuclei. On the other hand, DAergic cells of the periventricular nucleus of the hypothalamus and dorsal aspect of the arcuate nucleus, revealed by TH in situ hybridization, did not exhibit NTR mRNA even though dense NT binding sites have been previously described in this nuclei. In the zona incerta, TH mRNA-containing cells were concentrated in the medial part, with little overlap with NTR mRNA-expressing cells located mainly in its mediolateral extent. In contrast, the distribution of both markers was superimposable within the different subdivisions of the ventral tegmental area and substantia nigra, as previously suggested, but also in the retrorubral field. These anatomical data further support the NT-dopamine interactions on both mesocorticolimbic and nigrostriatal DAergic systems. Moreover, the results suggest that diencephalic DAergic neurons do not synthesize the cloned NTR mRNA or express it at considerably lower levels than DAergic mesencephalic cells.