Imaging Neurotransmitter Uptake Sites in Brain
Dopamine is an important neurotransmitter, and like other catecholamine
neurotransmitters, its action at the synapse is thought to be terminated by reuptake.
The dopamine reuptake carrier or transporter is a drug receptor for cocaine since the
binding of cocaine to this transporter appears to correlate with the reinforcing
properties of cocaine (Science 237:1219-1223, 1987). In order to study the transporter
in vivo, in vivo labeling receptor ligands and techniques have been developed.
Several cocaine analogues have a high affinity for the dopamine transporter in in
vitro binding studies. These ligands are potent behaviorally as well. Because of their
high in vitro affinity, they were examined for their suitability as in vivo labeling
ligands. 3H-WIN 35,428 preferentially accumulates at dopamine transporters in vivo.
The ligand appears to be a superb one since its specific to nonspecific binding ratios are
higher than for any other transporter ligand. RTI-55 is an iodinated cocaine analogue
that also binds effectively in vivo. It has the advantage of being an iodinated ligand and
therefore a promising candidate for SPECT scanning.
Utilization of these ligands allow measurement of cocaine receptors in vivo and an
estimation of the rate of occupancy of receptors by a variety of drugs.
Kuhar, MJ., Scheffel, U., Boga, J., Carroll, F., Shaya, E., Wong, D., ... Cline, E. (1992). Imaging Neurotransmitter Uptake Sites in Brain. International journal of radiation applications and instrumentation. Part B, Nuclear medicine and biology, 16(1), 116. DOI: 10.1016/0883-2897(92)90204-C