Autoradiographic evidence for the localization of high affinity neurotensin binding sites on dopaminergic nerve terminals in the nigrostriatal and mesolimbic pathways in rat brain.

Monoiodo[125I]Tyr3-neurotensin binding in coronal and sagittal brain sections from rats that had received a unilateral 6-hydroxydopamine lesion of the median forebrain bundle, revealed a complete loss of neurotensin binding (NTH)-sites in the caudate nucleus of the lesioned side. Moreover, in the lesioned side, 83% of the NTH-sites disappeared also from the nucleus accumbens and 65% from the olfactory tubercle. NTH-sites subsisted partly in the Islands of Calleja and no significant alteration was observed in the rhinal sulcus and in the cingulate cortex. We conclude that, in the terminal area of the nigrostriatal pathway, all functional NTH-sites are located on presynaptic dopaminergic nerve endings. In the terminal areas of the mesolimbic pathway, the vast majority of NTH-sites are also located on dopaminergic nerve endings. Only a few NTH-sites may possibly be located on non-dopaminergic nerve endings in the olfactory tubercle. NTH-sites can therefore be considered as specific markers of the dopaminergic nerve terminals in both the nigrostriatal and mesolimbic pathways.