DASB, also known as 3-amino-4-(2-dimethylaminomethylphenylsulfanyl)-benzonitrile, is a compound that binds to the serotonin transporter. Labeled with carbon-11 — a radioactive isotope — it has been used as a radioligand in neuroimaging with positron emission tomography (PET) since around year 2000.[1] In this context it is regarded as one of the superior radioligands for PET study of the serotonin transporter in the brain,[2] since it has high selectivity for the serotonin transporter.[3]

Structural formulas
DASB (above) and [C-11]DASB
Space-filling model
Radioactive carbon atom marked in cyan
CAS Number
PubChem CID
Chemical and physical data
Molar mass283.39 g·mol−1
3D model (JSmol)
 ☒N☑Y (what is this?)  (verify)

The DASB image from a human PET scan shows high binding in the midbrain, thalamus and striatum, moderate binding in the medial temporal lobe and anterior cingulate, and low binding in neocortex. The cerebellum is often regarded as a region with no specific serotonin transporter binding and the brain region is used as a reference in some studies.[4]

Since the serotonin transporter is the target of SSRIs used in the treatment of major depression it has been natural to examine DASB binding in depressed patients. Several such research studies have been performed.[5]

There are a number of alternative PET radioligands for imaging the serotonin transporter: [11C]ADAM, [11C]MADAM, [11C]AFM, [11C]DAPA, [11C]McN5652, and [11C]-NS 4194. A related molecule to DASB, that can be labeled with fluorine-18, has also been suggested as a PET radioligand.[6] With single-photon emission computed tomography (SPECT) using the radioisotope iodine-123 there are further radioligands available: [123I]ODAM, [123I]IDAM, [123I]ADAM,[7] and [123I]β-CIT.[2] A few studies have examined the difference in binding between the radioligands in nonhuman primates,[8][9] as well as in pigs.[10]

Other compounds that can be labeled to work as PET radioligands for the study of the serotonin system are, e.g., altanserin and WAY-100635.

Methodological issuesEdit

The binding potential of DASB can be estimated with kinetic modeling on a series of brain scans.[11]

A test-retest reproducibility PET study indicates that [11C]DASB can be used to measure the serotonin transporter parameters with high reliability in receptor-rich brain regions.[4]

When the DASB neuroimages are analyzed the kinetic models suggested by Ichise and coworkers[12] can be employed to estimate the binding potential. A test-retest reproducibility experiment has been performed to evaluate this approach.[13]


Besides the studies listed below a few occupancy studies have been reported.[5]

DASB binding neuroimaging studies (patients compared to healthy control subjects).
What Result Subjects Ref.
5-HTTLPR LALA serotonin transporter genotype Increase in putamen 43/30 [14]
5-HTTLPR LALA serotonin transporter genotype Increase in midbrain 19 [15]
5-HTTLPR LALA serotonin transporter genotype No difference 63 [16]
Age No effect found [17] ([2])
Body mass index Inverse correlation (?) ? [18]
Seasonality Higher in winter in putamen and caudate 54 [19]
Seasonality Higher in fall and winter 88 [20]
NEO PI-R Neuroticism Positive correlation in thalamus 31 males [21]
Depressed during major depressive episodes No difference found 20+20 [17]
Depressed with highly negativistic "dysfunctional attitudes" during major depressive episodes Increase in prefrontal cortex, anterior cingulate, thalamus, bilateral caudate, and bilateral putamen 20(?)+20 [17]
Recovered depressed patients No difference found 24+20 males [22]
Unipolar depression Increase in thalamus, insula and striatum 18+34 [23]
Unmedicated unipolar major depression Reduced 5-HTT availability in the thalamus [24]
TCI anxiety in unmedicated unipolar major depression Reduced 5-HTT availability in the thalamus, midbrain and amygdala [24]
Bipolar depression Increase in thalamus, insula and striatum 18+34 [23]
Bipolar depression Decrease in midbrain, amygdala, hippocampus, thalamus, putamen, and anterior cingulate cortex 18+41 [25]
Obsessive compulsive disorder Reduction and correlation with severity in thalamus and midbrain 9+19 [26]
Alcoholism No significant alteration 30 + 18 [27]
Parkinson's disease Reduction in forebrain 5+8 [28]
Non-depressed Parkinson's disease Decreased binding in caudate, midbrain, putamen, orbitofrontal cortex and (non-significantly) dorsolateral prefrontal cortex [29]
Depressed Parkinson's disease patients Increase in prefrontal and dorsolateral cortices 7+7 [30]
Abstinent MDMA ('Ecstasy') users Global reduction 23+19 [31]
Former MDMA users and polydrug users No significant difference in brain regions examined 12+9+19 [32]
Reduced synaptic serotonin (by rapid tryptophan depletion) (small reduction in binding potential) 8 [33]
Lowering of brain serotonin (by acute tryptophan depletion) No change observed 25 (14) [34]


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