Stereoselective behavioral effects of Lu 19-005 in monkeys: relation to binding at cocaine recognition sites

Chiral Resolution of the Enantiomers of the Slow-Onset Dopamine Reuptake Inhibitor CTDP-32476 and Their Activities

An improved synthesis was developed for CDTP-32476, a potent slow-onset dopamine reuptake blocker that may have utility as a treatment for cocaine abuse. The enantiomers of the compound were separated by fractional crystallization with N-acetylleucine enantiomers. An X-ray crystal structure was obtained of the RR enantiomer paired with N-acetyl-d-leucine. Chiral chromatography showed that the resolved enantiomers were pure with little contamination by the other enantiomer. The enantiomers were tested for their ability to block the reuptake of monoamines at their respective transporters and to stimulate locomotor activity in mice. Both enantiomers potently blocked the reuptake of dopamine and stimulated locomotor activity in mice. The RR enantiomer that corresponds to the active RR enantiomer of methylphenidate was slightly more potent at the dopamine reuptake site. The RR enantiomer also was found to be about twice as selective for the dopamine transporter relative to the norepinephrine transporter, which may have clinical implications. A method for designing slow-onset stimulants is proposed since there is increasing evidence that such activity is an important factor in stimulants that may have limited abuse potential.

Enantioselective and Regiodivergent Copper-Catalyzed Electrophilic Arylation of Allylic Amides with Diaryliodonium Salts

A catalytic enantioselective and regiodivergent arylation of alkenes is described. Chiral copper(II)bisoxazoline complexes catalyze the addition of diaryliodonium salts to allylic amides in excellent ee. Moreover, the arylation can be controlled by the electronic nature of the diaryliodonium salt enabling the preparation of nonracemic diaryloxazines or β,β'-diaryl enamides.

Indatraline: synthesis and effect on the motor activity of Wistar rats

A new approach for the synthesis of indatraline was developed using as the key step an iodine(III)-mediated ring contraction of a 1,2-dihydronaphthalene derivative. Behavioral tests were conducted to evaluate the effect of indatraline and of its precursor indanamide on the motor activity of Wistar rats. Specific indexes for ambulation, raising and stereotypy were computed one, two and three hours after i.p. drug administration. Indatraline effects on motor activity lasted for at least three hours. On the other hand, no significant differences in motor activity were observed using indanamide. The results suggest that indatraline has a long lasting effect on motor activity and add evidence in favor of the potential use of that compound as a substitute in cocaine addiction.

A slow-onset, long-duration indanamine monoamine reuptake inhibitor as a potential maintenance pharmacotherapy for psychostimulant abuse: effects in laboratory rat models relating to addiction

Slow-onset, long-lasting dopamine reuptake blockers with reduced abuse potential have been suggested as maintenance therapies for cocaine addiction. We have synthesized a series of 3-(3',4'-dichlorophenyl)-1-indanamine monoamine reuptake inhibitors as candidates for such maintenance pharmacotherapy. The initial lead compound, the N,N-dimethyl analogue 30,640 was then subjected to testing in addiction-relevant animal models. Compound 30,640 (2 mg/kg i.p.) produced a pronounced slow-onset, long-lasting increase (300-400%) in extracellular nucleus accumbens dopamine levels, as measured by in vivo brain microdialysis in awake laboratory rats. Slow-onset, long-lasting decreases (40-80%) in the dopamine metabolites 3,4-dihydroxyphenylacetic acid and homovanillic acid, and the serotonin metabolite 5-hydroxyindoleacetic acid were also seen. Compound 30,640 (3 or 5 mg/kg i.p.) also produced a significant (approximately 30%) slow-onset, long-lasting enhancement of electrical brain-stimulation reward, which was additive with that of cocaine (5 mg/kg i.p.). When given to cocaine-administering rats, 30,640 (2.5, 3, 5, or 10 mg/kg i.p.) significantly inhibited (30-60%) intravenous cocaine self-administration, with a pronounced long-lasting profile. In sum, 30,640 showed cocaine-like effects, but with a marked slow-onset, long-lasting profile. We conclude that the prodrug strategy employed in the design of 30,640 achieved its goal. We suggest that such compounds may be useful as maintenance pharmacotherapies for psychostimulant addiction.

Slow-onset, long-duration 3-(3',4'-dichlorophenyl)-1-indanamine monoamine reuptake blockers as potential medications to treat cocaine abuse

A series of 3-(3',4'-dichlorophenyl)-1-indanamine monoamine reuptake blockers have been synthesized in an effort to develop a compound that could be used as a maintenance therapy to treat cocaine abuse. Since the effects of cocaine on dopamine (DA) and serotonin (5HT) transporters are important components of its pharmacological activity, the focus was on nonselective inhibitors of monoamine transport. To reduce or eliminate the abuse potential of a DA reuptake blocker, the compounds were designed to be slow-onset, long-duration prodrugs whose N-demethylated metabolites would have increased activity over the parent compound with the ideal being a parent compound that has little or no activity. To achieve this, pairs of compounds with different groups on the amine nitrogen and with and without an additional N-methyl group were synthesized. All of the synthesized compounds were screened for binding and reuptake at the cloned human DA, 5HT, and norepinephrine (NE) transporters. As previously found, trans isomers are nonselective blockers of DA, 5HT, and NE reuptake, cis isomers with small N-alkyl groups are selective blockers of 5HT reuptake, and tertiary amines of the trans compounds are less potent than the corresponding N-demethylated secondary amines as blockers of DA reuptake. Larger N-alkyl groups in both the trans and cis series were found to reduce activity for the 5HT and NE transporters with less effect at DA transporters. Selected trans compounds were also screened for locomotor activity in mice and generalization to a cocaine-like profile in rats. With intraperitoneal administration, all of the trans isomers showed a slow onset of at least 20 min and an extremely long duration of action in the locomotor assays. Several of the trans compounds also fully generalized to a cocaine-like pharmacological profile. An initial lead compound, the N,N-dimethyl analogue trans-1b, was resolved into chirally pure enantiomers. Surprisingly, both enantiomers were found to have significant affinity for the DA transporter and to cause locomotor activation. This is in contrast to the N-methyl compound in which only the (+)-enantiomer had significant activity. The absolute configuration of the more active enantiomer was determined by X-ray crystallography to be 3R,1S.

Prolonged dopamine and serotonin transporter inhibition after exposure to tropanes

Cocaine and tropane analogs are known to interact with biogenic monoamine transporters by inhibiting amine uptake. Previous in vivo studies have demonstrated that some of these tropanes produce a longer lasting behavioral effect compared with cocaine. We have previously examined several tropane analogs and found a difference in their relative affinities for dopamine (DA) and serotonin (5-HT) transporters. The purpose of this study was to determine the recovery time of transporter function in vitro and in vivo comparing cocaine with the tropane analogs WF-11 (PTT, selective for DA transporters), WF-31 (selective for 5-HT transporters) and WF-23 (highly potent at both DA and 5-HT transporters). In vitro, using primary rat brain cultures of either midbrain or raphe regions, the recovery of the ability to transport either [3H]dopamine or [3H]serotonin, respectively was evaluated at 0, 3, 24, 48, 120 and 240 h after a 1 h exposure to cocaine and tropane analogs. The tropanes exhibited clearance half-lives ranging from 12 to 69 h, while cocaine, on the other hand, exhibited a clearance half-life of approximately 6 h. In studies utilizing [125I]RTI-55 binding, intraperitoneal injections of cocaine and WF-23 into the rat resulted in striatal clearance half-lives ex vivo that were almost identical to those obtained in vitro. These data suggest that the tropanes bind to and reduce transporter function for prolonged periods of time (up to 10-fold longer than cocaine) and those compounds with the highest affinity may produce a pseudo-irreversible inhibition of transporter function.

The dopamine transporter carboxyl-terminal tail. Truncation/substitution mutants selectively confer high affinity dopamine uptake while attenuating recognition of the ligand binding domain

In order to delineate structural motifs regulating substrate affinity and recognition for the human dopamine transporter (DAT), we assessed [3H]dopamine uptake kinetics and [3H]CFT binding characteristics of COS-7 cells transiently expressing mutant DATs in which the COOH terminus was truncated or substituted. Complete truncation of the carboxyl tail from Ser582 allowed for the expression of biphasic [3H]dopamine uptake kinetics displaying both a low capacity (Vmax approximately 0.4 pmol/10(5) cells/min) high affinity (Km approximately 300 nM) component and one exhibiting low affinity (Km approximately 15 microM] and high capacity (Vmax approximately 5 pmol/10(5)cells/min) with a concomitant 40% decrease in overall apparent Vmax relative to wild type (WT) DAT. Truncation of the last 22 amino acids or substitution of the DAT-COOH tail with sequences encoding the intracellular carboxyl-terminal of either dopamine D1 or D5 receptors produced results that were identical to those with the fully truncated DAT, suggesting that the induction of biphasic dopamine uptake kinetics is likely conferred by removal of DAT-specific sequence motifs distal to Pro597. The attenuation of WT transport activity, either by lowering levels of DAT expression or by pretreatment of cells with phorbol 12-myristate 13-acetate (1 microM), did not affect the kinetics of [3H]dopamine transport. The estimated affinity of dopamine (Ki approximately 180 nM) for all truncated/substituted DAT mutants was 10-fold lower than that of WT DAT (approximately 2000 nM) and appears selective for the endogenous substrate, since the estimated inhibitory constants for numerous putative substrates or uptake inhibitors were virtually identical to those obtained for WT DATs. In marked contrast, DAT truncation/substitution mutants displayed significantly reduced high affinity [3H]CFT binding interactions with estimated Ki values for dopamine and numerous other substrates and inhibitors tested from 10-100-fold lower than that observed for WT DAT. Moreover, co-expression of truncated and/or substituted DATs with WT transporter failed to reconstitute functional or pharmacological activities associated with both transporters. Instead, complete restoration of uniphasic low affinity [3H]dopamine uptake kinetics (Km approximately 2000 nM) and high affinity substrate and inhibitor [3H]CFT binding interactions attributable to WT DATs were evident. These data clearly suggest the functional independence and differential regulation of the dopamine translocation process from the characteristics exhibited by its ligand binding domain. The lack of functional phenotypic expression of mutant DAT activities in cells co-expressing WT transporter is consistent with the contention that native DATs may exist as multisubunit complexes, the formation and maintenance of which is dependent upon sequences encoded within the carboxyl tail.

N-[1-(2-Benzo(b)thiophenyl)cyclohexyl]piperidine (BTCP) and cocaine induce similar effects on striatal dopamine: a microdialysis study in freely moving rats

N-[1-(2-Benzo(b)thiophenyl)cyclohexyl]piperidine (BTCP) and cocaine inhibit dopamine (DA) uptake but bind to different sites on the transporter. Their dose-dependent effects (i.p. administration) on extracellular DA levels in the rat striatum were measured by in vivo microdialysis. Both drugs dose-dependently increased DA levels with a maximum effect 60 min post injection. BTCP (20 mg/kg) had a greater peak effect than cocaine (40 mg/kg). For doses inducing similar behavioral effects (cocaine, 20mg/kg; BTCP, 10 mg/kg) similar DA increases were observed in the striatum and the nucleus accumbens. Although both drugs bind on the DA transporter on different sites and induce different behavioral effects when administered chronically, their acute administration increased striatal DA level in a similar way.

Translocation of dopamine and binding of 2 beta-carbomethoxy-3 beta-(4-fluorophenyl) tropane (WIN 35,428) measured under identical conditions in rat striatal synaptosomal preparations. Inhibition by various blockers

Translocation of [3H]dopamine and binding of 2 beta-carbomethoxy-3 beta-(4-fluorophenyl)[3H]-tropane ([3H]WIN 35,428) were measured in crude synaptosomal preparations from rat striatum under identical conditions of assay buffer (phosphate-Krebs) and temperature (25 degrees). [3H]Dopamine uptake as a function of time was close to linear for at least 8 min, whereas [3H]WIN 35,428 binding had reached equilibrium within 1 min and remained at its plateau value for at least 20 min. The following inhibitors were tested in uptake and binding assays run in parallel with the same synaptosomal preparation: cocaine, WIN 35,428, benztropine, nomifensine, mazindol, methylphenidate, N-[1-(2-benzo[b]-thiophenyl)cyclohexyl]piperidine (BTCP), Lu 19-005 (Indatraline), 1-(2-(di(4-fluorophenyl)-methoxy)-ethyl)-4-(3-phenyl-2-propyl)piperazine (GBR 12909), 1-(2-(diphenylmethoxy)-ethyl)-4-(3-phenyl-2-propyl)piperazine (GBR 12935) and 7-trifluoromethyl-4-(4-methyl-1-piperazinyl)-pyrrolo [1,2-a]quinoxaline (CGS 12066B). When present together with [3H]dopamine or [3H]WIN 35,428 for 8 min, the observed binding IC50 values were generally higher (average 1.4-fold) than the uptake IC50 values, with a significant y-axis intercept in linear regression analysis of binding on uptake IC50. For slowly equilibrating inhibitors, estimates of uptake IC50 values were overestimates, and relatively lower values were obtained by monitoring [3H]dopamine uptake for 1 min only during the last minute of the 8-min presence of inhibitor; under these conditions, binding over uptake IC50 ratios were on the average 2.3. Kinetic calculations, taking into account both radioligand and inhibitor equilibration kinetics, indicated that the latter comparison between binding and uptake measurements was most relevant, and suggested the involvement of complexities beyond simple competitive inhibition of dopamine transport, such as different binding domains for substrate and blocker recognition, or spare receptors for blockers. The present data indicate that binding over uptake IC50 ratios should be interpreted with caution, depending on the experimental conditions used to measure these ratios.

Cocaine accumulates in dopamine-rich regions of primate brain after i.v. administration: comparison with mazindol distribution

Pharmacological and neurochemical evidence suggest that brain dopamine systems, and the dopamine transporter in particular, contribute significantly to the behavioral effects and reinforcing properties of cocaine. The first objective of this study was to determine whether the brain distribution of cocaine supports these conclusions. A high resolution neuroanatomical map of cocaine disposition in brain after i.v. administration was developed. [3H]Cocaine ([3H](-)-cocaine) was administered to squirrel monkeys (Saimiri sciureus) at a trace dose (0.001 mg/kg) and at doses at or above the threshold for producing behavioral effects (0.1 mg/kg, 0.3 mg/kg). After 15 min, ex vivo autoradiography revealed the highest accumulation of [3H]cocaine in dopamine-rich brain regions, including the caudate nucleus, putamen, and nucleus accumbens/olfactory tubercle. The norepinephrine-rich locus coeruleus, the hippocampus, and amygdala also accumulated large quantities of [3H]cocaine. Moderately high levels were found in the stria terminalis, medial septum, substantia nigra, and other regions. Lowest levels were found in the cerebellum. A high and positive correlation was established for the brain distribution of [3H]cocaine administered at trace or at behaviorally relevant doses (r: 0.94; P < 0.001). To determine whether radioactivity represented [3H]cocaine or its metabolic products, tissue extracts from brain regions with high levels of cocaine were subjected to thin layer chromatography using two solvent systems. In caudate-putamen, nucleus accumbens, cortex, and hippocampus, radioactivity comigrated with standard [3H]cocaine. In substantia nigra, less than 70% of the radioactivity comigrated with [3H]cocaine, suggesting that cocaine metabolites are generated more rapidly in the substantia nigra than in other brain regions. The second objective was to determine the brain distribution of mazindol, a potent norepinephrine and dopamine transport inhibitor with low abuse liability in humans. The disposition of intravenously administered [3H]mazindol in brain (0.001 mg/kg, 0.007 mg/kg) was surveyed by ex vivo autoradiography. In sharp contrast to [3H]cocaine distribution, the highest accumulation of [3H]mazindol was localized in the norepinephrine-rich pineal gland, discrete regions of the hypothalamus (paraventricular nucleus, supraoptic nucleus), and the locus coeruleus. Moderately high levels were detected in the caudate-putamen, nucleus accumbens, and other regions. The following conclusions were drawn: (1) Although dopamine-rich brain regions are principal targets of cocaine after i.v. administration to the nonhuman primate, other prominent targets of cocaine (locus coeruleus, hippocampus, and amygdala) may contribute to the acute and chronic effects of cocaine.(ABSTRACT TRUNCATED AT 400 WORDS)

[3H]WIN 35,428 binding to the dopamine uptake carrier. I. Effect of tonicity and buffer composition

In the present study, the dopamine transporter on rat striatal membranes was labeled with [3H]WIN 35,428 (2 beta-carbomethoxy-3 beta-(4-fluorophenyl)-tropane), and its binding state or form was manipulated by changing tonicity and buffer composition. Binding to P2 membranes was enhanced by the presence of sucrose in the assay. This effect was not due solely to factors relating to tonicity because creation of isotonicity by dextrose or N-methyl-D-glucamine was less effective, and an increase in binding by sucrose was also observed in assays that were already isotonic by a mixture of sodium phosphate and NaCl. Under the latter conditions, fructose and mannose were equally effective as sucrose. Other important factors were the presence of sodium phosphate in the homogenizing buffer and the presence of sucrose during resuspension of the membranes. When P2 membranes were prepared from homogenates in 0.32 M sucrose, the effect of sucrose in the polytronning step or in the binding assay was restricted to a decrease in the Kd of the main binding component.

[3H]WIN 35,428 binding to the dopamine uptake carrier. II. Effect of membrane fractionation procedure and freezing

In the present study the dopamine transporter on rat striatal membranes was labeled with [3H]WIN 35,428 (2 beta-carbomethoxy-3 beta-(4-fluorophenyl)-tropane) and its binding state or form was compared between fresh and frozen tissue fractionated by various protocols. Freezing striatal tissue resulted in a decrease in binding to crude or P2 membranes, but did not consistently generate upward concave Scatchard plots. Among various conditions, sodium phosphate buffers containing sucrose, employed for homogenization and for measurement of binding to freshly prepared P2 membranes, were most likely to give multiple binding component resolutions. These results allow us to reconcile the existing literature on [3H]WIN 35,428 binding and to identify (1) the 'universal' binding component common to all studies thus far, (2) a high-affinity component measured with sufficiently low ligand concentration, and (3) a low-affinity component observed with sufficiently high ligand concentration.