| Assay Method Information | |
| | h-SERT Binding Assay |
| Description: | The [3H] citalopram binding was measured according to the method disclosed in Owens M. J. et al., J. Pharm. Exp. Ther., 283, 1305-1322 (1997). In specific, a solution of 200 μL in total was prepared by mixing 50 μL of [3H] citalopram (manufactured by GE Healthcare) diluted with a SERT buffer (final concentration: about 2 nmol/L), 149 μL of the h-SERT/CHO membrane preparation (protein amount: 40 μg/well), and 1 μL of the test drug dissolved in dimethylsulfoxide. The solution was reacted at room temperature for 60 minutes, and then quickly suction-filtered under reduced pressure through a glass fiber filter coated with 0.05% aq. polyethyleneimine. The glass fiber filter was washed twice with 250 HL of the SERT buffer, placed in a plastic vial containing 4 mL of liquid scintillator (ACS-II, manufactured by Amersham) or Ecoscint A (manufactured by National Diagnostics), and the remaining radioactivity on the filter paper was assayed with a liquid scintillation counter. The non-specific binding of [3H] citalopram was defined as a binding amount in the presence of 1 μmol/L clomipramine (manufactured by Sigma Aldrich) The IC50 value was calculated according to Hill analysis [see, Hill A. V., J. Physiol., 40, 190-200 (1910)], and the binding inhibition constant (Ki) was calculated according to the following formula: Binding inhibition constant (Ki)=IC50/(1+S/Kd) wherein S is a concentration of the added [3H] citalopram, and Kd is a binding dissociation constant of [3H] citalopram which was calculated from a saturated binding assay using the same cell membrane. A lower Ki value (i.e. a lower h-SERT binding inhibition constant) means that the test drug has a stronger human serotonin reuptake inhibitory action. |
| Affinity data for this assay | |
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