In pharmacokinetics and receptor-ligand kinetics the binding potential (BP) is a combined measure of the density of "available" neuroreceptors and the affinity of a drug to that neuroreceptor.
The binding potential is then the ratio ligand-receptor complex to free ligand at equilibrium and in the limit of L tending to 0, and is given symbol BP:
This quantity, originally defined by Mintun,[1] describes the capacity of a receptor to bind ligand.
It is a limit (L << Ki) of the general receptor association equation:
These equations apply equally when measuring the total receptor density or the residual receptor density available after binding to second ligand - availability.
BP is a pivotal measure in the use of positron emission tomography (PET) to measure the density of "available" receptors, e.g. to assess the occupancy by drugs or to characterize neuropsychiatric diseases (yet, one should keep in mind that binding potential is a combined measure that depends on receptor density as well as on affinity).
[2] Estimating BP with PET usually requires that a reference tissue is available.
A reference tissue has negligible receptor density and its distribution volume should be the same as the distribution volume in the target region if all receptors were blocked.
Generally, if there were no arterial samples ("noninvasive imaging"), BP denotes
In PET imaging, the amount of radioligand is usually very small (L << Ki, see above), thus
: Transfer rate constants from the two tissue compartment model.
In Innis et al.,[3] a large group of researchers who are active in this field agreed to a consensus nomenclature for these terms, with the intent of making the literature in this field more transparent to non-specialists.
The convention involves use of the subscripts p for quantities referred to plasma and ND for quantities referred to the free plus nonspecifically bound concentration in brain (NonDisplaceable).