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DASB – in vitro binding characteristics on human recombinant monoamine transporters with regard to its potential as positron emission tomography (PET) tracer
Author(s) -
Hummerich René,
Reischl Gerald,
Ehrlichmann Walter,
Machulla HansJürgen,
Heinz Andreas,
Schloss Patrick
Publication year - 2004
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2004.02585.x
Subject(s) - serotonergic , serotonin transporter , human brain , monoamine neurotransmitter , neuroscience , positron emission tomography , serotonin , neurotransmitter , chemistry , biology , biochemistry , receptor , central nervous system
Abstract The efficiency of serotonergic signal transduction is controlled by the density of serotonegic synapses and by the activity of the serotonin transporter (SERT), which selectively clears the synaptic cleft of the neurotransmitter. SERT is located in axons, where it is concentrated in varicosities and terminal boutons and thus is an exquisite marker for serotonergic synapses. This finding has been taken advantage of for neuroimaging serotonergic synaptic contact sites. Previous positron emission tomography (PET) and single photon emission computed tomography (SPECT) studies were often carried out using radioligands that bind with high affinity to SERTs in the brainstem but also exhibit high affinity for dopamine and norepinephrine transporters and therefore did not allow quantification of serotonergic innervations in brain regions also containing dopaminergic or noradrenergic terminals. In order to visualize SERT availability more selectively, in recent years new tracers have been developed, one of which is [ 11 C]DASB ( N , N ‐dimethyl‐2‐2‐amino‐4‐cyanophenylthiobenzylamine). Here, we have performed a detailed pharmacological characterization of unlabelled as well as radioactive DASB on recombinant human monoamine transporter proteins. Our results show that DASB selectively binds to SERT with high affinity ( K D = 3.5 n m ) to a site distinct from the serotonin (5‐HT) recognition/translocation site. 5‐HT inhibits DASB binding to SERT with more than one order of magnitude lower affinity than that of DASB binding (IC 50 = 82.4 n m ). These findings suggest DASB to be a highly selective PET tracer to visualize the density of serotonergic synapses in human brain.