Quantitative in vitro autoradiography of neurotransmitter receptors - Applications to diseased human brains.

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Abstract
The technique of in vitro autoradiography is widely utilized for observations of specific binding sites of neurotransmitters of drugs. The current trend of this research field is toward quantifying receptor densities in auto-radiograms of brain sections. In this paper, the authors showed the method for quantification in our laboratory and confirmed that receptor densities obtained from in vitro autoradiography almost consisted with those from receptor binding assay. Since in vitro autoradiography can construct high-resolution maps of receptor distributions, it is the useful tool for studies of neural functions. The authors performed the quantitative in vitro autoradiography in diseased human brains. Two cases of late cortical cerebellar atrophy (LCCA) were used in these experiments. Through morphometric analysis, it was observed that Purkinje cells in both case 1 and 2 were lost in half as many as those in control cases and the density of the granular cells was markedly reduced in the cerebellar cortex of case 2. In the dentate nucleus of case 1, the increase of GABA receptors as well as the decrease of GABA concentration was observed and this increase is considered to be receptor supersensitivity. In addition, the reduction of glutamate binding sites was observed in the dentate nucleus of both cases. Neurobiological basis of this receptor change is left for further investigations.