Estimation of D2-like receptor occupancy by dopamine in the putamen of hemiparkinsonian Monkeys.

Published

Journal Article

To advance understanding of the neurochemical changes in Parkinson's disease (PD), we compared D2-like dopamine receptor occupancy by dopamine in the control and lesioned putamen of four pig-tailed macaques treated unilaterally with MPTP. PET and in vitro binding techniques were used to measure binding potential (BP(*)) and density of D2-like dopamine receptors (B(max)), respectively. As would be expected in PD, relatively higher values of BP(*) and B(max) and less amphetamine-induced decrease in [(11)C]raclopride binding were observed in the lesioned compared with the contralateral putamen in each animal. The percent differences between lesioned and contralateral sides were similar whether the measurements were of [(11)C]raclopride BP(*) or B(max) values, measured in vivo and in vitro, respectively. As [(11)C]raclopride BP(*) is a measure of the density of D2-like dopamine receptors available for radioligand binding (i.e., not occupied by dopamine), these findings suggest that the fractional occupancy of receptors by endogenous dopamine in the lesioned putamen is nearly equal to that in the contralateral putamen. Therefore, the absolute number of receptors occupied by dopamine, which is a product of receptor density and fractional occupancy by dopamine, is greater in the lesioned than in the contralateral putamen. One possible explanation for the lack of differences in fractional occupancy of D2 receptors by dopamine (despite a loss in available dopamine) is a lesion-induced increase in a portion of low-affinity D2 receptors to a state of high affinity for dopamine.

Full Text

Duke Authors

Cited Authors

  • Chefer, SI; Kimes, AS; Matochik, JA; Horti, AG; Kurian, V; Shumway, D; Domino, EF; London, ED; Mukhin, AG

Published Date

  • January 2008

Published In

Volume / Issue

  • 33 / 2

Start / End Page

  • 270 - 278

PubMed ID

  • 17429408

Pubmed Central ID

  • 17429408

Electronic International Standard Serial Number (EISSN)

  • 1740-634X

International Standard Serial Number (ISSN)

  • 0893-133X

Digital Object Identifier (DOI)

  • 10.1038/sj.npp.1301404

Language

  • eng