3H]2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalen (ADTN). Regional distribution and in vivo binding after acute and chronic drug treatment.

Abstract

The regional distribution and in vivo binding of the dopamine analog 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalen (ADTN) was studied in the brain. The highest density of binding sites was in the striatum, with virtually no binding in the cerebellum. The binding of [3H]ADTN reflects an occupation of specific dopamine sites because the binding was diminished by the simultaneous administration of the dopamine antagonist haloperidol or the dopamine precursor L-3,4-dihydroxyphenylalanine (L-dopa). Chronic administration of haloperidol or L-dopa prior to assaying for in vivo binding resulted in an increase in the number of sites for [3H]ADTN which correlates to the increase observed in in vitro assays following long-term treatment with these agents. The subcellular distribution of in vivo labeled ADTN sites in the caudate nucleus indicate a high density of specific binding sites in the microsomal fraction, P3. Overall, these data demonstrate that the aminotetralins, such as ADTN, which bind with high affinity to the dopamine receptor in the caudate nucleus in vitro and in vivo, can provide precise information on the topography of this receptor.