Table 2.
Receptor occupancies achieved by [11C]FPEB and [11C]SP203 at time of peak specific binding in three brain regions.
| Brain region | mGluR5 Bmax (nM)a | Peak brain concentration (nM) |
% Occupancy at peak brain concentration |
Peak specific brain concentration (nM)b |
% Occupancy at peak specific brain concentrationc |
||||
|---|---|---|---|---|---|---|---|---|---|
| [11C]FPEB | [11C]SP203 | [11C]FPEB | [11C]SP203 | [11C]FPEB | [11C]SP203 | [11C]FPEB | [11C]SP203 | ||
| Frontal cortex | 25 ± 5.6 | 3.4 ± 1.0 | 1.2 ± 0.3 | 13 ± 4.1 | 4.9 ± 1.4 | 3.0 ± 1.0 | 1.1 ± 0.4 | 12 ± 3.9 | 4.2 ± 1.4 |
| Caudate | 17 ± 2.3 | 3.1 ± 1.0 | 1.2 ± 0.3 | 18 ± 5.6 | 7.0 ± 2.0 | 2.6 ± 1.0 | 1.0 ± 0.3 | 15 ± 5.7 | 5.8 ± 2.0 |
| Cerebellum | 5.1 ± 2.0 | 2.8 ± 0.9 | 1.0 ± 0.3 | 55 ± 17 | 19 ± 5.9 | 1.4 ± 0.5 | 0.5 ± 0.2 | 27 ± 10 | 10 ± 3.0 |
Data are mean ± SD from eight subjects for [11C]FPEB and six subjects for [11C]SP203.
a
Bmax values are from Patel et al.26 and assume that 10 mg brain contains 1 mg protein.
b
The concentration of specific binding came from the two-tissue compartment model, which separates radioligand into specific and nondisplaceable compartments.
c
Occupancy for each region was calculated by dividing peak specific concentration by its Bmax.