Autoradiographic distribution of [3H]neurotensin receptors in rat brain: visualization by tritium-sensitive film.

[3H]Neurotensin ([3H]NT) binds specifically to a single class of binding sites on slides-mounted sections of rat brain 1Kp = 5.1 nM; Bmax = 16.2 fmol/mg tissue). Bound [3H]NT can be displaced by nonradioactive NT and a series of its fragments and analogues with relative potencies that correlate closely (r = 0.89; p less than 0.01) to their potencies in the rat stomach strip bioassay. These results suggest that NT receptors are similar in both systems. [3H]NT binding sites were visualized by using tritium-sensitive LKB film analysed by computerized densitometry. [3H]NT receptors are highly concentrated in the external layer of the olfactory bulb, in the rhinal sulcus, in certain nuclei of the amygdala, in the substantia nigra, zona compacta and in the ventral tegmental area. The high density of [3H]NT receptors in the last two areas suggest an interaction between NT and brain dopaminergic systems such as the nigrostriatal and the mesolimbic pathways.