Sequential H(2)(15)O PET studies in baboons: before and after amphetamine

Area of Science:

• Neuroscience
• Radiochemistry
• Pharmacology

Background:

• Positron Emission Tomography (PET) with (11)C-raclopride is used to measure dopamine activity.
• This method relies on d-amphetamine (AMPH) to induce dopamine release.
• A key assumption is that cerebral blood flow (CBF) remains constant during PET scans.

Purpose of the Study:

• To evaluate the impact of AMPH administration on sequential PET measurements of CBF.
• To determine if CBF variations affect the accuracy of dopamine activity assessment.

Main Methods:

• Six baboons underwent dynamic H(2)(15)O PET scans before and after AMPH administration (0.6 mg/kg).
• Arterial blood sampling and MRI-defined regions of interest (cortex, striatum, cerebellum) were used.
• CBF was quantified using a 1-tissue compartment model (K(1)).

Main Results:

• AMPH administration induced transient increases in CBF (K(1)) across various brain regions in most baboons.
• These CBF alterations, though statistically significant in some areas, were deemed unlikely to substantially affect (11)C-raclopride binding potential.
• Anesthesia-induced variability was minimized to enhance in vivo measure reliability.

Conclusions:

• The study supports the assumption of stable CBF in (11)C-raclopride/AMPH PET experiments.
• It highlights the necessity of accounting for anesthesia effects when interpreting in vivo imaging parameters.
• Results validate prior PET studies assuming constant blood flow.