ABSTRACT
This chapter illustrates the many opportunities available for imaging drug action and for monitoring therapy at the neuroreceptor sites using positron emission tomography (PET) or single photon emission computed tomography (SPECT) procedures. The principles of imaging of neuroreceptors had their origins in in vitro binding studies of the 1970s. The potential for this methodology gained plausibility with the development of receptor autoradiography. PET imaging of opiate receptors was first reported in 1985 by Frost et al; the radioligand was C-carfentanil. This potent opiate agonist is highly selective for the mu opiate receptor subtype. PET scanning and a related technique, SPECT, are in a general class of tomographic methods for imaging the regional distribution of radiotracers. These radiotracers are incorporated into compounds of biological interest in order to describe the chemistry of the biological process being studied. In all cases, an attempt is made to label a chemical compound with a radioisotope such that the tracer principle is maintained.
