Autoradiographic comparison of D1-specific binding of [3H]SCH39166 and [3H]SCH23390 in the primate cerebral cortex.
Quantitative autoradiography was used to compare the binding of the novel dopamine D1 receptor antagonist, [3H]SCH39166, with that of the widely used radioligand, [3H]SCH23390 (in the presence of ritanserin), in the primate cerebral cortex. Specific binding of both radioligands, determined using SCH23390 or cis-flupentixol as displacing agents, had very similar densities and distributions throughout the cortex. However, the specific binding of [3H]SCH39166 obtained with SCH39166 as a blank was significantly higher than that obtained using SCH23390 or cis-flupentixol as displacing agents in some layers of motor, somatosensory and occipital cortices. In addition, the non-specific binding of [3H]SCH39166 obtained in the presence of an excess of SCH23390 of cis-flupentixol displayed a complex laminar pattern very different from that of the specific binding. These observations suggest that [3H]SCH39166 may have a high affinity to more than the D1 receptor subtype bound by SCH23390 or cis-flupentixol. Also, these additional sites are likely to be different from 5-HT2 or 5-HT1C receptors since the latter sites were not displaced by 1 microM SCH23390.
Lidow
M S
MS
Yale University School of Medicine, Section of Neuroanatomy, New Haven, CT 06510.
Goldman-Rakic
P S
PS
Rakic
P
P
Gallager
D W
DW
D000818:Animals; D001345:Autoradiography; D001552:Benzazepines / Q000378:metabolism*; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000378:metabolism*; D018492:Dopamine Antagonists; D005475:Flupenthixol / Q000378:metabolism; D008253:Macaca mulatta; D011954:Receptors, Dopamine / Q000378:metabolism*
D001552:Benzazepines; D018492:Dopamine Antagonists; D011954:Receptors, Dopamine; C058081:ecopipam; D005475:Flupenthixol