In this case, for each receptor, we sum the npKi values at each receptor across each of the thirty-five drugs.
npKi values below about 2.0 should be imperceptible, while values above about 2.0 should be perceptible, and the higher the npKi value, the more perceptible a receptor should be at a particular drug.
npKi values below about 2.0 should be imperceptible, while values above about 2.0 should be perceptible, and the higher the npKi value, the more perceptible a receptor should be.
An index of the breadth (or inverse of selectivity), B, of the binding profiles of the individual drugs or receptors can be constructed by summing the forty-two npKi values for each drug, or the thirty-five npKi values for each receptor.
In Fig. 3, a black vertical bar represent a 100-fold drop in affinity relative to the receptor with the highest affinity, and divides those npKi values greater than 2.0 (on the left) from those 2.0 or less (on the right).
Table S5 and Table S6 present the raw Ki data converted into npKi values, for both the individual receptors, and groups of receptors summed using the Bsq statistic.
Thus, receptors with npKi values below about 2.0 should not have perceptible mental effects.
It is not clear that a simple sum of npKi values is the best index of breadth.
Table 4 shows for each drug, the lowest Ki value measured (KiMin) which is the best-hit, the best-hit receptor (KiMinR), the theoretically lowest measurable npKi value (npKiLim), the lowest actually measured npKi value (npKiMin), and the receptor where the lowest npKi value was actually measured (npKiMinR).
For these drugs, the range of Ki values that can be measured by the NIMH-PDSP is less than the 100-fold presumed perceptible range, and therefore, the lowest measurable npKi value is greater than the presumed limit of perceptibility at 2.00.
