Binding experiments of muscarinic acetylcholine and dopamine receptors in human brains with emphasis on a case of striatonigral degeneration.

In the regional distribution of I-3H-quinuclindinyl benzilate (3H-QNB) binding in human brains of neurologically unaffected cases, it was highest in the caudate nucleus which was followed by the putamen, amygdala, cerebral corteces and olfactory bulb and lowest in the substantia nigra. As to the regional distribution of 3H-spiroperidol binding in human control brains, it was highest in the caudate nucleus and was followed by the cerebral corteces, amygdala and lowest in the cerebellar cortex. In a case of striatonigral degeneration (SND), 3H-QNB binding in the putamen and thalamus was lowered and 3H-spiroperidol binding was decreased in the putamen, frontal and parietal corteces, Ammon's horn, amygdala and substantia nigra as compared to human brains of control cases. These results were noteworthy since no pathological changes were observed in the thalamus, cerebral corteces, amygdala and Ammon's horn in this case. The 3H-spiroperidol binding was increased by injection of 6-hydroxydopamine (6-OHDA) into the substantia nigra of rat brains by 17% as compared to the contralateral intact side. Conversely, 3H-spiroperidol binding was decreased by injection of kainic acid (KA) into the striatum of rat brains by 43% as compared to the contralateral intact side. This meant that dopamine receptors labelled by 3H-spiroperidol were at least partially localized at the postsynaptic site of the nigrostriatal dopamine neuron.