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.

Endogenous Neurotensin in the Ventral Tegmental Area Contributes to Amphetamine Behavioral Sensitization

“…NT-immunoreactive dense core vesicles are visible near segments of somatodendritic and nerve terminal plasma membrane, suggesting that NT may be released from dendrites as well as from nerve terminals (Bayer et al, 1991). The NT1 receptor is found chiefly in DA midbrain neurons, but a small proportion is associated with non-DA axons and astroglial cells (Nicot et al, 1995;Boudin et al, 1998). Although NT2-receptor expression on glial cells has been shown by in situ hybridization (Sarret et al, 1998;Walker et al, 1998), immunohistochemistry studies suggest a strong association of NT2 receptor with neurons, and predominantly with their dendritic arbors (Sarret et al, 2003).…”

Role of Calcium in Neurotensin-Evoked Enhancement in Firing in Mesencephalic Dopamine Neurons

“…DAergic neurons express NTS1 protein and mRNA (Nicot et al, 1995;Boudin et al, 1998). Considering the coupling of this receptor to PLC and IP 3 production (Bozou et al, 1989;Tanaka et al, 1990;Hermans et al, 1992), the hypothesis that its activation causes intracellular Ca 2ϩ elevation in DAergic neurons is reasonable but was untested.…”

Repeated Administration of the Neurotensin Receptor Antagonist SR 48692 Differentially Regulates Mesocortical and Mesolimbic Dopaminergic Systems

“…It may be hypothesized that SR 48692 regulates the release of DA by acting directly on DA neurons of the VTA, which express high levels of NT receptors (Szigethy and Beaudet, 1989;Nicot et a!., 1995). Thus, the SR 48692-induced decrease in basal release of DA might be due to its antagonism of NT receptors located on DA cell bodies, where NT has been shown previously to stimulate electrical activity of DA neurons (Shi and Bunney, 1991;Stowe and Nemeroff, 1991), as well as DA release and turnover in the nucleus accumbens (Kalivas et al, 1983;Cador et a!., 1989;Ford and Marsden, 1990;Kalivas and Duffy, 1990;Laitinen et a!., 1990;Rivest et a!., 1991;Steinberg et a!., 1994.…”