The VNTR polymorphism
in the human dopamine transporter gene: improved detection and absence of
association of VNTR alleles with attention-deficit hyperactivity disorder.
Simsek M, Al-Sharbati M,
Al-Adawi S,
Lawatia K.
Department of Biochemistry, College of Medicine, Sultanate of Oman. mssimsek@omantel.net.om
The human dopamine transporter (DAT1) gene contains a variable number
tandem repeat (VNTR) in its 3'-untranslated region because of repetition of
a 40-bp core sequence. Methods available for the diagnosis of this
polymorphism are limited in number. We have developed a new polymerase
chain reaction (PCR) test, which is similar to that described originally by
Vandenbergh's group, but provides a better
detection of the VNTR alleles in the human DAT1 gene. Using two independent
PCR methods, we have determined the distribution of VNTR alleles in 110
healthy Omani subjects, and in 92 children with attention-deficit
hyperactivity disorder (ADHD). The frequency of the risk allele (DAT1*10)
was similar in the healthy subjects and ADHD cases, indicating absence of
association of this allele with ADHD in Oman.
PMID: 16545000 [PubMed - in process]
Interaction of cis-(6-benzhydrylpiperidin-3-yl)benzylamine analogues with monoamine
transporters: structure-activity relationship study of structurally
constrained 3,6-disubstituted piperidine
analogues of
(2,2-diphenylethyl)-[1-(4-fluorobenzyl)piperidin-4-ylmethyl]amine.
Kolhatkar
RB, Ghorai
SK, George C, Reith ME, Dutta
AK.
Wayne State University, Department of Pharmaceutical
Sciences, Detroit, Michigan 48202, USA.
To explore structure-activity relationships (SAR) of a novel conformationally constrained lead cis-3,6-disubstituted piperidine
derivative derived from
(2,2-diphenylethyl)-[1-(4-fluorobenzyl)piperidine-4-ylmethyl]amine (I), a
series of compounds was synthesized by derivatizing
the exocyclic N-atom at the 3-position of the
lead. This study led to the formation of substituted phenyl and
heterocyclic derivatives. All novel compounds were tested for their
affinity at the dopamine transporter (DAT), serotonin transporter (SERT),
and norepinephrine transporter (NET) in the brain
by measuring their potency in competing for the binding of [3H]WIN 35 428,
[3H]citalopram, and [3H]nisoxetine,
respectively. Selected compounds were also evaluated for their activity in
inhibiting the uptake of [3H]DA. The SAR results
demonstrated that the nature of substitutions on the phenyl ring is
important in activity at the DAT with the presence of an
electron-withdrawing group having the maximum effect on potency.
Replacement of the phenyl ring in the benzyl group by heterocyclic moieties
resulted in the development of compounds with moderate activity for the
DAT. Two most potent racemic compounds were
separated by a diastereoisomeric separation
procedure, and differential affinities were observed for the enantiomers. Absolute configuration of the enantiomers was obtained unambiguously by X-ray crystal
structural study. One of the enantiomers,
compound S,S-(-)-19a, exhibited the highest
potency for the DAT (IC50 = 11.3 nM) among all
the compounds tested and was as potent as GBR 12909 (1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine). However, the compound (-)-19a was more
selective than GBR 12909 in binding to the DAT compared with binding to the
SERT and NET. The present results establish the newly developed 3,6-disubstituted piperidine
derivatives as a novel template for high-affinity inhibitors of DAT.
Structurally these molecules are more constrained compared to our earlier
flexible piperidine molecules and, thus, should
provide more insights about their bioactive conformations.
PMID: 12747792 [PubMed - indexed for MEDLINE]
Studies
of the biogenic amine transporters. XI. Identification of a 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine
(GBR12909) analog that allosterically modulates
the serotonin transporter.
Nightingale B,
Dersch
CM, Boos TL, Greiner E,
Calhoun WJ,
Jacobson AE,
Rice KC, Rothman RB.
Clinical Psychopharmacology Section, Intramural Research Program, National
Institute on Drug Abuse, National Institutes of Health, 5500 Nathan Shock
Drive, Baltimore, MD 21224, USA.
Previous studies identified partial inhibitors of serotonin (5-HT)
transporter and dopamine transporter binding. We report here on a partial
inhibitor of 5-HT transporter (SERT) binding identified among a group of
1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine analogs (4-[2-[bis(4-fluorophenyl)-methoxy]ethyl]-1-(2-trifluoromethyl-benzyl)-piperidine; TB-1-099). Membranes were prepared from rat
brains or human embryonic kidney cells expressing the cloned human dopamine
(hDAT), serotonin (hSERT),
and norepinephrine (hNET)
transporters. beta-(4'-(125)Iodophenyl)tropan-2beta-carboxylic
acid methyl ester ([(125)I]RTI-55) binding and other assays followed
published procedures. Using rat brain membranes, TB-1-099 weakly inhibited
DAT binding (K(i) = 439 nM), was inactive at NET binding ([(3)H]nisoxetine), and partially inhibited SERT binding with
an extrapolated plateau ("A" value) of 20%. Similarly, TB-1-099
partially inhibited [(125)I]RTI-55 binding to hSERT with an extrapolated plateau (A value) of 14%.
Upon examining the effect of increasing concentrations of TB-1-099 on the
apparent K(d) and B(max) of [(125)I]RTI-55 binding to hSERT,
we found that TB-1-099 decreased the B(max) in a dose-dependent manner and
affected the apparent K(d) in a manner well described by a sigmoid
dose-response curve. TB-1-099 increased the K(d)
but not to the magnitude expected for a competitive inhibitor. In rat brain
synaptosomes, TB-1-099 noncompetitively inhibited
[(3)H]5-HT, but not [(3)H]dopamine, uptake.
Dissociation experiments indicated that TB-1-099 promoted the rapid
dissociation of a small component of [(125)I]RTI-55
binding to hSERT. Association experiments
demonstrated that TB-1-099 slowed [(125)I]RTI-55
binding to hSERT in a manner unlike that of the
competitive inhibitor indatraline. Viewed
collectively, these results support the hypothesis that TB-1-099 allosterically modulates hSERT
binding and function.
Development of
long-acting dopamine transporter ligands as
potential cocaine-abuse therapeutic agents: chiral
hydroxyl-containing derivatives of 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine
and 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)piperazine.
Hsin
LW, Dersch
CM, Baumann MH,
Stafford D,
Glowa
JR, Rothman RB,
Jacobson AE,
Rice KC.
Laboratory of Medicinal Chemistry, National Institute of
Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
In our search for long-acting agents for the treatment of cocaine abuse, a
series of optically pure hydroxylated derivatives
of 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (1) and 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)piperazine (2) (GBR 12909 and GBR 12935, respectively)
were synthesized and evaluated in vitro and in vivo. The enantiomers of the 2-hydroxylated analogues displayed
substantial enantioselectivity. The S enantiomers displayed higher dopamine transporter (DAT)
affinity and the R enantiomers were found to
interact at the serotonin transporter (SERT) with higher affinity. The
two-carbon spacer between the hydroxyl group and the piperazine
ring was essential for enantioselectivity, and
the length of the alkyl chain between the phenyl group and the piperazine ring influenced binding affinity and
selectivity for the DAT and SERT. Phenylethyl
analogues had a higher binding affinity for the SERT and a weaker affinity
and selectivity for the DAT than the corresponding phenylpropyl
analogues. Thus, (S)-(+)-1-[4-[2-[bis(4-fluorophenyl)methoxy]ethyl]piperazinyl]-3-phenylpropan-2-ol (6) displayed the
highest affinity to the DAT, and (S)-(+)-1-[4-[2-(diphenylmethoxy)ethyl]piperazinyl]-3-phenylpropan-2-ol (8) had the highest
selectivity. The latter (8) is one of the most DAT selective ligands known. In accord with the in vitro data, 6
showed greater potency than 7 in elevating extracellular
dopamine levels in a microdialysis assay and in
inhibiting cocaine-maintained responding in rhesus monkeys.
PMID: 11882001 [PubMed - indexed for MEDLINE]
Synthesis and dopamine
transporter affinity of chiral 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(2-hydroxypropyl)piperazines
as potential cocaine abuse therapeutic agents.
Hsin
LW, Prisinzano
T, Wilkerson CR,
Dersch
CM, Horel
R, Jacobson AE,
Rothman RB,
Rice KC.
Laboratory of Medicinal Chemistry, National Institute of
Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
A series of optically pure phenyl-and non-phenyl-substituted 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(2-hydroxypropyl)piperazines
was synthesized and their binding affinity for dopamine transporter (DAT)
was investigated. The analogues with a hydroxyl group in the S
configuration were more selective for the DAT over the serotonin
transporter (SERT) than the corresponding R enantiomers.
Compound (+)-11 showed high affinity and selectivity for DAT over the SERT
and, therefore, is a potential candidate for the development of a
long-acting cocaine abuse therapeutic agent.
PMID: 12565970 [PubMed - indexed for MEDLINE]
Cocaine abuse 
