Autoradiographic localization of 5-HT(2A) receptors in the human brain using [(3)H]M100907 and [(11)C]M100907.
M100907 (MDL 100907, R-(+)-alpha-(2, 3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidinemethanol++ +) is a new selective antagonist of 5-HT(2A) receptors. The compound has been labeled with (11)C and proved useful for in vivo studies of 5-HT(2A) receptors using positron emission tomography (PET). In the present study the distribution of 5-HT(2A) receptors was examined in the postmortem human brain using whole hemisphere autoradiography and [(3)H]M100907 and [(11)C]M100907. The autoradiograms showed very dense binding to all neocortical regions, whereas the hippocampus was only weakly labeled with [(3)H]M100907. Other central brain regions, such as the basal ganglia and thalamus, showed low [(3)H]M100907 binding, reflecting low densities of 5-HT(2A) receptors. The cerebellum or structures of the brain stem were virtually devoid of 5-HT(2A) receptors. [(11)C]M100907 gave images qualitatively similar to those of [(3)H]M100907, although with lower spatial resolution. The labeling of human 5-HT(2A) receptors with [(3)H]M100907 was inhibited by the addition of the 5-HT(2A) receptor blockers ketanserin or SCH 23390 (10 microM), leaving a very low background of nonspecific binding. The 5-HT(1A) receptor antagonist WAY-100635 and the D(2)-dopamine receptor antagonist raclopride had no effect on the binding of [(3)H]M100907. The selective labeling of 5-HT(2A) receptors with [(3)H]M100907 clearly shows that this compound is suitable for further studies of the human 5-HT(2A) receptor subtype in vitro. The in vitro autoradiography of the distribution of 5-HT(2A) receptors obtained with radiolabeled M100907 provides detailed qualitative and quantitative information on the distribution of 5-HT(2A)-receptors in the human brain as well as reference information for the interpretation of previous initial results at much lower resolution in humans in vivo with PET and [(11)C]M100907.
Hall
H
H
Karolinska Institutet, Department of Clinical Neuroscience, Psychiatry Section, Karolinska Hospital, S-17176 Stockholm, Sweden. hakan.hall@psyk.ks.se
Farde
L
L
Halldin
C
C
Lundkvist
C
C
Sedvall
G
G
D000328:Adult; D001345:Autoradiography; D001921:Brain / Q000378:metabolism*; D002250:Carbon Radioisotopes; D005260:Female; D005464:Fluorobenzenes / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019579:Neocortex / Q000378:metabolism; D010880:Piperidines / Q000378:metabolism*; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000378:metabolism*; D014018:Tissue Distribution; D014316:Tritium
D002250:Carbon Radioisotopes; D005464:Fluorobenzenes; D010880:Piperidines; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D014316:Tritium; C079049:volinanserin