ABSTRACT
The neuroreceptor concept is based on the observation that exogenous drugs can influence brain function by a specific association with membrane or cytosolic proteins designed to receive endogenous neurotransmitters or neuromodulators. The kinetic description of receptor-ligand interaction followed the discovery of the association between oxygen and myoglobin. In vitro, the receptors bind the ligand after the death of the organism and in autora-diography, dehydration, or fixation of the tissue. In vitro, the analysis of the neuroreceptor-ligand interaction can be made with high specific activity and excess radioligand. “Residue detection” is the method of measuring the quantity of tracer left in the target organ at a given moment during circulation, in contrast to the previous methods of “inflow-outflow” detection in which arterial and venous concentrations were measured. Radioligands sequester within the tissue with the result that they escape the build-up in the extracellular space that leads to backflux.
