P02-357 - In vivo molecular imaging reveals distinct distributions of the serotonin transporter, the major inhibitory and excitatory serotonin receptors

Abstract

IntroductionBased on evidences in molecular neuroimaging, postmortem and genetic studies, impaired serotonergic neurotransmission has been implicated with affective disorders. Moreover, a growing number of evidences showed strong interrelations within the serotonergic system suggesting a common mechanism in the modulation of receptor and transporter densities.ObjectiveHere we directly investigated the regional expression of the 5-HT1A, 5-HT2A and 5-HTT using PET and the three highly selective and specific radioligands [carbonyl-11C]WAY-100635, [18F]Altanserin and [11C]DASB in healthy subjects.MethodsA total of 55 healthy subjects (5-HT1A: 36 subjects, 18 males, age = 26.0 ± 4.9; 5-HT2A: 19 subjects, 11 males, age = 28.2 ± 5.9; 5-HTT: 8 males, age = 28.12 ± 3.6) were included in this study. Binding potential (BPND) values were quantified according to the AAL parcellation scheme.ResultsBPND values averaged over both hemispheres ranged from 0.40–6.35 for the 5-HT1A receptor; 0.01–2.01 for the 5-HT2A receptor and 0.09–2.05 for the 5-HTT, respectively. There was a specific topological pattern according to the ratio between the 5-HT1A, 5-HT2A receptors and 5-HTT (“fingerprints”).ConclusionsSuch information can be essential for detecting potential local alterations in the ratio between different binding proteins on a network level in pathological conditions.Moreover, these data might provide further insight in area-specific effects of frequently prescribed selective serotonin re-uptake inhibitors (SSRI): 1)due to the distinct local receptor and transporter availability;2)SSRI application alters the postsynaptic receptor expression and thus;3)leads to a modified interaction of inhibitory and exhibitory receptors.