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Radiotracer Administration for High Temporal Resolution Positron Emission Tomography of the Human Brain: Application to FDG-fPET
Published on: October 22, 2019
Receptor occupancy and brain free fraction
Jeanette Watson1, Sara Wright, Adam Lucas
1Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Sir James Black Centre, Dundee, DD1 5EH, Scotland, UK.
Brain unbound concentration (C(u,brain)) better predicts dopamine D(2) receptor occupancy in rats than other measures. This finding is crucial for understanding antipsychotic drug efficacy and brain penetration.
Area of Science:
- Pharmacology
- Neuroscience
- Drug Discovery
Background:
- Dopamine D(2) receptors are key targets for antipsychotic medications.
- Accurate prediction of receptor occupancy is vital for optimizing drug efficacy and minimizing side effects.
- Current methods for predicting receptor occupancy have limitations.
Purpose of the Study:
- To evaluate brain unbound concentration (C(u,brain)) as a predictor of dopamine D(2) receptor occupancy.
- To compare C(u,brain) with total brain concentration, cerebrospinal fluid concentration (C(CSF)), and blood unbound concentration (C(u,blood)).
Main Methods:
- Ex vivo determination of D(2) receptor occupancy and concentration-time profiles for six antipsychotic drugs in rats.
- Oral administration of drugs across a range of dose levels.
- Estimation of C(u,brain) using total brain concentration and unbound fraction from a brain homogenate method.
Main Results:
- Brain unbound concentration (C(u,brain)) demonstrated a strong correlation with D(2) receptor occupancy.
- C(u,brain) provided a superior prediction of D(2) receptor occupancy compared to C(CSF) and C(u,blood).
- This improved prediction was particularly evident for drugs whose brain entry is not solely dependent on passive diffusion.
Conclusions:
- C(u,brain) is a valuable predictor of dopamine D(2) receptor occupancy in preclinical models.
- Understanding brain unbound concentrations aids in predicting antipsychotic drug performance.
- This approach offers enhanced insight into drug disposition and receptor engagement for centrally acting agents.
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