[3H]SCH 23390 labels both dopamine-1 and 5-hydroxytryptamine1c receptors in the choroid plexus.
[3H]SCH 23390 has been used to label the D-1 subtype of dopamine receptors. Quantitative autoradiographic studies with [3H]SCH 23390 have revealed high levels of binding in many regions of rat brain including the caudate-putamen, nucleus accumbens, substantia nigra and choroid plexus. The selectivity of the binding of [3H]SCH 23390 was characterized further in studies using homogenates of canine choroid plexus. Scatchard analysis of the binding of increasing concentrations of [3H]SCH 23390 resulted in a curvilinear plot when (+)-butaclamol was used to define specific binding. Nonlinear regression analysis of untransformed data was consistent with the presence of two distinct classes of binding sites. The high-affinity site (Kd, 0.4 nM) was present at low density (maximum binding sites, 30 fmol/mg of protein) and had the pharmacological properties expected of a D-1 receptor. The low-affinity site (Kd, 24 nM) was present at a much greater density (maximum binding sites, 350 fmol/mg of protein) and had the pharmacological properties expected of a 5-hydroxytryptamine1c receptor. Quantitative autoradiographic studies of the binding of [3H]SCH 23390 to sections of rat brain also suggested that 5-hydroxytroptamine1c receptors in the choroid plexus are labeled by [3H]SCH 23390. It is possible that [3H]SCH 23390 labels 5-hydroxytryptamine1c receptors in other brain regions as well.
Nicklaus
K J
KJ
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia.
McGonigle
P
P
Molinoff
P B
PB
D000818:Animals; D001345:Autoradiography; D001552:Benzazepines / Q000378:metabolism*; D001667:Binding, Competitive; D002831:Choroid Plexus / Q000032:analysis*; D004285:Dogs; D066298:In Vitro Techniques; D011954:Receptors, Dopamine / Q000032:analysis*; D017447:Receptors, Dopamine D1; D011985:Receptors, Serotonin / Q000032:analysis*; D012701:Serotonin / Q000494:pharmacology
D001552:Benzazepines; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D011985:Receptors, Serotonin; D012701:Serotonin