Related Experiment Videos
SPECT imaging with the D(4) receptor antagonist L-750,667 in nonhuman primate brain
J K Staley1, G Tamagnan, R M Baldwin
1Department of Psychiatry, Yale University School of Medicine & VA Connecticut Healthcare System, West Haven, Connecticut, USA. julie.staley@yale.edu
Nuclear Medicine and Biology
|November 1, 2000
Summary
The radiotracer [(123)I]L750,667 showed brain uptake in nonhuman primates but failed to bind dopamine D(4) receptors in vivo. This indicates it is not suitable for imaging D(4) receptors.
Area of Science:
- Radiochemistry
- Neuroscience
- Medical Imaging
Background:
- Dopamine D(4) receptors are implicated in various neurological disorders.
- Developing selective radiotracers for in vivo imaging is crucial for understanding receptor function and disease states.
Purpose of the Study:
- To evaluate the suitability of [(123)I]L750,667 as a radiotracer for single photon emission computed tomography (SPECT) imaging of dopamine D(4) receptors in nonhuman primates.
Main Methods:
- [(123)I]L750,667 was synthesized via iododestannylation and administered to baboons.
- SPECT imaging was performed for 6 hours post-administration.
- The effect of a D(4) receptor antagonist (NGD 94-1) on tracer uptake was assessed.
Main Results:
- [(123)I]L750,667 demonstrated significant uptake in various brain regions, peaking at 15 minutes postinjection.
- Uptake was observed across the diencephalon, brainstem, basal ganglia, cingulate cortex, and cerebellum.
- Administration of NGD 94-1 did not displace radioactivity from any brain regions, despite receptor-saturating doses.
Conclusions:
- While L750,667 exhibits in vitro selectivity for D(4) receptors, [(123)I]L750,667 is not suitable for in vivo imaging of these receptors.
- The lack of displacement by NGD 94-1 suggests poor in vivo target engagement or insufficient tracer affinity at effective doses.