a higher binding potential in the temporal lobe of the patients with PD compared to the healthy controls.86 Similarly, [11 C]MPDX was used for mapping of the A1Rs in the brain of aged human compared to the young subjects and showed a significantly lower BPND in the frontal, temporal, occipital, parietal cortices, and thalamus of aged subjects.87 [11 C]MPDX is currently the most widely used PET agent for imaging the A1Rs in human brain.83,85 Interestingly, [11 C]MPDX was employed to identify the selective antagonists (DPCPX and caffeine) and agonist (N6-cyclopentyladenosine [CPA]) binding sites on the A1Rs and suggested that different ligands (agonists and/or antagonists) bind to A1Rs allosterically.88
