In vivo characterization of a novel phenylisothiocyanate tropane analog at monoamine transporters in rat brain.
Previous studies have shown that the phenylisothiocyanate tropane analog 2-beta-propanoyl-3-beta-(2-naphthyl)-8-[4-isothiocyanato)benzyl]nortropane (HD-205) binds covalently to dopamine and serotonin transporters (DAT and SERT, respectively) in rat brain membranes (Biochem Pharmacol 74:336-344, 2007). The present study evaluated the irreversible effects of HD-205 in vivo in rats after intracranial injection. Rats were implanted with unilateral cannulae in rat striatum, and HD-205 (0.001-3 nmol) was administered by intrastriatal injection. In vitro autoradiography of DAT binding with [125I]2-carbomethoxy-3-(4-iodophenyl)tropane (RTI-55) on brain sections obtained 24 h after injection showed a highly localized blockade of binding in striatum, with maximal blockade of binding by 1 to 3 nmol HD-205. Similar blockade of SERT binding (using [3H]-citalopram) was observed in the same area. No blockade of DAT or SERT binding was observed after intrastriatal injections of the reversible analog 2-beta-propanoyl-3-beta-(2-naphthyl)-8-benzyl nortropane (HD-206), and HD-205 treatment had no effect on D(2)- and mu-opioid-stimulated guanosine 5'-O-(3-[35S]thio)-triphosphate binding in sections from the same animals. In a time course study, rats administered with 1 nmol HD-205 showed recovery of 50% DAT binding after 3 to 4 days postinjection, and full recovery after 6 weeks. Rats implanted with bilateral cannulae were tested for cocaine-induced locomotor activity. Two days after intrastriatal injection of 1 nmol of HD-205, systemic (20 mg/kg i.p.) cocaine-induced locomotor activity was not affected; however, locomotor activity induced by intrastriatal administration of cocaine (6 nmol) was eliminated. This strategy of site-specific chemical blockade of transporters could serve as a valuable tool to evaluate the neuroanatomical basis of DAT-mediated cocaine effects.
Murthy
Vishakantha
V
Department of Physiology/Pharmacology, Wake Forest University Health Sciences, Medical Center Blvd., Winston-Salem, NC 27157, USA.
Martin
Thomas J
TJ
Kim
Susy
S
Davies
Huw M L
HM
Childers
Steven R
SR
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003042:Cocaine / Q000494:pharmacology; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D017879:Isothiocyanates / Q000737:chemistry / Q000494:pharmacology*; D008297:Male; D015394:Molecular Structure; D009043:Motor Activity / Q000187:drug effects; D009662:Nortropanes / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D051381:Rats; D011916:Rats, Inbred F344; D050486:Serotonin Plasma Membrane Transport Proteins / Q000378:metabolism*; D014326:Tropanes / Q000737:chemistry / Q000494:pharmacology*
C530603:2-propanoyl-3-(2-naphthyl)-8-(4-isothiocyanatobenzyl)nortropane; C530604:2-propanoyl-3-(2-naphthyl)-8-benzylnortropane; D050483:Dopamine Plasma Membrane Transport Proteins; D017879:Isothiocyanates; D009662:Nortropanes; D050486:Serotonin Plasma Membrane Transport Proteins; D014326:Tropanes; C005441:phenylisothiocyanate; D003042:Cocaine