Loss of high affinity neurotensin receptors in substantia nigra from parkinsonian subjects

Monoiodo[ 125I-Tyr 3]-Neurotensin binding was studied in post mortem substantia nigra from 17 control and 15 parkinsonian subjects. Binding to individual homogenates was decreased by 58 %, 49 % and 26 % at 0.36, 1.4, 5.5 M −9 concentration of ligand, respectively. Saturation analysis using pooled substantia nigra demonstrated an almost complete loss of the high affinity component of the neurotensin receptor complex, yielding a 24 % loss of the total binding capacity, with no alteration of the low affinity component. Similarly an important loss of binding was observed in monoiodo[ 125I-Tyr 3]-Neurotensin autoradiograms of two substantia nigra from parkinsonian subjects. These results support the hypothesis of neurotensin receptors occuring on dopamine cell bodies and/or dendrites in human substantia nigra. Role of neurotensin may be of importance in the regulation of dopamine pathway involved in parkinsonism.