RT Journal Article SR Electronic T1 Measurement of the proportion of serotonin 1A receptors configured in high affinity state: A comparison PET study using agonist radioligand [11C]CUMI-101 and antagonist radiotracer [11C]WAY-100635 in vivo in baboons JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1222 OP 1222 VO 50 IS supplement 2 A1 Vattoly J Majo A1 Jaya Prabhakaran A1 Matthew Millak A1 Lyudmila Savenkova A1 Ronald L van Heertum A1 John J Mann A1 Ramin V Parsey A1 Dileep Kumar YR 2009 UL http://jnm.snmjournals.org/content/50/supplement_2/1222.abstract AB 1222 Objectives [11C]CUMI-101 is a 5-HT1A receptor agonist tracer suitable to image 5-HT1A receptors configured in high affinity state. In this study, in vivo binding of [11C]CUMI-101 was assessed with PET in baboons and compared to that of the antagonist radiotracer [11C]WAY-100635. Methods Male baboons were studied with [11C]WAY-100635 followed by [11C]CUMI-101 under baseline conditions. Kinetic modeling with an arterial input function was used to derive the specific-to-nonspecific equilibrium partition coefficients. The binding potential were determined by the following equation, BPF = (VT – VND)/fP = Bmax/KD; BPP = VT – VND = fP Bmax/KD; BPND = (VT – VND)/VND = fND Bmax/KD, where VND and VT are defined as the distribution volumes of the nondisplaceable and total (ND + specific) compartments, respectively. Results [11C]WAY-100635 BPF were in the range of 55, 45, 41 respectively for hippocampus, insula, cingulate regions. The corresponding [11C]CUMI-101 BPF were in the range of 28, 26, 24 respectively. Conclusions In general, a marked decrease in BPF were observed for [11C]CUMI-101 scans in comparison with the corresponding [11C]WAY-100635 scans for 5-HT1A receptor–rich regions.