Autoradiographic mapping of dopamine-D2/D3 receptor stimulated [35S]GTPgammaS binding in the human brain.
Agonist stimulated [35S]guanosine 5'-gamma-thiotriphosphate ([35S]GTPgammaS) binding autoradiography was established for the examination of dopamine-D2/D2 receptors in human brain sections. The distribution of G proteins activated by dopamine-D2/D3 receptors was studied in whole hemisphere cryosections. Dopamine stimulated [35S]GTPgammaS binding in brain regions with high densities of dopamine D2-like receptors, i.e. putamen (23 +/- 2%, mean +/- SEM,% stimulation over basal binding), caudate (20 +/- 0%) and substantia nigra (22 +/- 2%), but also in regions with lower receptor densities such as amygdala (17 +/- 8%), hippocampus (16 +/- 6%), anterior cingulate (13 +/- 3%), and thalamus (12 +/- 2%). Dopamine stimulated [35S]GTPgammaS binding to significantly higher levels in the dorsal than in the ventral part of the striatum. Dopamine caused low or very low stimulation in all cortical areas. Raclopride, a selective D2/D3 receptor antagonist, potently inhibited dopamine stimulated [35S]GTPgammaS binding, whereas R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride (SCH23390), a selective D1 antagonist, did not block the [35S]GTPgammaS binding response stimulated by dopamine. Hence, the stimulatory effect of dopamine was primarily mediated by D2/D3 receptors. Quinpirole stimulated [35S]GTPgammaS binding in the same regions as dopamine. The maximal level of stimulation induced by dopamine and quinpirole was not significantly different. The present study demonstrates that agonist stimulated [35S]GTPgammaS binding autoradiography could be a suitable technique for the examination of dopamine-D2/D3 receptors in the human brain. This functional assay could provide useful new information about dopamine receptor/G protein coupling in the postmortem human brain, and reveal possible disease related alterations of the interaction between D2/D3 receptors and G proteins.
Sóvágó
Judit
J
Karolinska Institutet, Department of Clinical Neuroscience, Psychiatry Section, Karolinska Hospital, S-17176, Stockholm, Sweden.
Makkai
Boglárka
B
Gulyás
Balázs
B
Hall
Håkan
H
D000328:Adult; D000368:Aged; D001345:Autoradiography / Q000379:methods; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D001931:Brain Mapping / Q000379:methods; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D011869:Radioligand Assay / Q000379:methods; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000378:metabolism*; D050637:Receptors, Dopamine D3; D013462:Sulfur Radioisotopes; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
C493593:DRD3 protein, human; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D013462:Sulfur Radioisotopes; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019204:GTP-Binding Proteins; D004298:Dopamine