1-[1-(2-Benzo[b]thiopheneyl)cyclohexyl]piperidine hydrochloride (BTCP) yields two active primary metabolites in vivo. Identification and quantification of BTCP primary metabolites in mice plasma, urine, and brain and their affinity for the neuronal dopamine transporter.

1-[1-(2-Benzo[b]thiopheneyl)cyclohexyl]piperidine hydrochloride (BTCP) and cocaine bind to the neuronal dopamine transporter (DAT) to strongly inhibit dopamine (DA) reuptake. Although similar to acute administration, cocaine and BTCP produce sensitization and tolerance, respectively, on chronic administration. We previously found that liver microsomes produced two primary metabolites from BTCP with a high affinity for DAT. Because such metabolites, if produced in vivo, could account for the pharmacological difference with cocaine, it was important to compare BTCP biotransformations in vitro and in vivo. Therefore, we identified and quantified BTCP and primary metabolites in mice urine, plasma, and brain after acute i.p. administration. The low recovery yield suggest that BTCP might behave like its close analogue, phencyclidine, with long-term storage of metabolites. Two active metabolites found in vitro were found in mice brain with estimated half-life values similar to that of BTCP (0.3 h). Although respective brain concentrations were 20 and 40 times lower than that of BTCP, their potency to displace in vivo [³H]BTCP bound to the DAT was 50 and 10 times higher, respectively, than that of BTCP. They could, therefore, contribute to the inhibition of DA transport and play an important role in BTCP pharmacology. They could also explain the differences between BTCP and cocaine on repeated administration.     

Synthesis of high specific activity (3,4-[3H]cyclohexyl)-N-[1 (2-benzo[b]thienyl)cyclohexyl]piperidine {[3H]BTCP}: A selective probe for the dopamine-reuptake complex

High specific activity [³H]BTCP, a radioligand for the dopaminereuptake complex was synthesized in 7-steps starting with the readily available starting materials, cyclohexane-1,4-dione monoethylene ketal and benzo[b]thiophene; the tritium label was introduced in the final step on the 3- and 4- positions of the cyclohexyl ring by catalytic tritiation of N-[4-(2-benzo[b]thienyl)cyclohexenyl]piperidine to give [³H]BTCP in 7.3% yield with a specific activity of 29.8 Ci/mmol (51.4% isotopic incorporation).     

Modulation by dopamine of [3H]N-[1-(2-benzo(b)thiophenyl)cyclohexyl]piperidine ([3H]BTCP, a phencyclidine derivative) binding to the dopamine uptake complex.

The modulation by dopamine of the binding of [3H]BTCP to the dopamine (DA) uptake complex was investigated in vivo (in control, reserpine- and L-DOPA-treated mice) and in vitro (on membrane preparations of the striatum of the rat). In both cases increasing doses of DA exerted a non-competitive inhibition of binding of [3H]BTCP, with a Ki value close to its K0.5, determined in competition experiments. Amphetamine and cocaine were also non-competitive inhibitors of the binding of [3H]BTCP, while GBR 12783 was competitive. In the presence of DA, the amount of cocaine required to inhibit the binding of [3H]BTCP was increased both in vitro and in vivo. These results suggest that inhibitors of the uptake of DA, such as BTCP or GBR 12783, modulate allosterically the uptake of DA, by binding to a site different from the DA recognition site. Cocaine, however, seems to share the same recognition site as DA.     

Pharmacological characterization of the discriminative stimulus properties of the phencyclidine analog, N-[1-(2-benzo(b)thiophenyl)-cyclohexyl]piperidine

Rationale: Although both cocaine and the phencyclidine analog, BTCP, have dopamine (DA) re-uptake blocking properties, under some conditions their behavioral effects can be differentiated. Therefore, we examined whether the discriminative stimulus (DS) effects of BTCP are different from those of cocaine. Objectives: To compare the effects of monoamine re-uptake blockers, varying in their in vitro potencies as inhibitors of DA, norepinephrine (NE), or serotonin re-uptake, in different groups of rats trained to discriminate either BTCP or cocaine from saline. Additionally, drugs from other pharmacological classes were tested in both groups. Methods: Rats were trained to discriminate either BTCP (5 mg/kg, i.p.) or cocaine (10 mg/kg, i.p.) from saline under a two-lever FR10 drug discrimination procedure. Results: BTCP and cocaine cross-substituted in BTCP- and cocaine-trained rats. The DA re-uptake blockers, mazindol, indatraline, methylphenidate, GBR12909, and GBR12935, occasioned dose-related drug-lever (DL) selection both in cocaine- and in BTCP-trained rats, with potencies that were significantly correlated. In contrast, the NE re-uptake blockers, nisoxetine, desipramine, and nortriptyline, produced higher levels of DL selection in BTCP-trained rats than in cocaine-trained rats, a profile like that reported in low-dose cocaine-trained rats. Drugs from other classes acted similarly in both discriminations. Further, the α₁-adrenergic antagonist prazosin dose dependently blocked the DS effects of the training dose of BTCP, but not of cocaine. Conclusions: Theresults suggest that the DS effects of BTCP are similar to cocaine, and resemble those of a low training dose of cocaine. Received: 6 October 1998 / Final version: 19 March 1999     

3H]N-[1-(2-benzo(b)thiophenyl)cyclohexyl]piperidine ([3H]BTCP): a new phencyclidine analog selective for the dopamine uptake complex

A benzothiophenyl group instead of a phenyl ring on phencyclidine (PCP) yields a molecule N-[1-(2-benzo(b)thiophenyl)cyclohexyl]piperidine (BTCP), which is one of the more potent known dopamine (DA) uptake inhibitors (IC50 = 7 nM). This compound also has low affinity for the PCP receptor (K0.5 = 6 microM). The sodium-dependent [3H]BTCP binding to rat striatal membranes was investigated. [3H]BTCP bound to two different sites: one with very high affinity (Kd1 = 0.9 nM, Bmax1 = 3.5 pmol/mg protein) which paralleled the distribution of dopaminergic nerve endings and a second with lower affinity (Kd2 = 20 nM, Bmax2 = 7.5 pmol/mg protein). There was a good correlation between the abilities of drugs specific for the DA uptake complex and of PCP analogs to inhibit high affinity [3H]BTCP binding and [3H]DA synaptosomal uptake. This study also demonstrated that PCP interacts with the DA uptake site since it is a competitive inhibitor of high affinity [3H]BTCP binding. This site, however, is not the PCP receptor, which has a different pharmacological selectivity.     

Design, synthesis, and biological evaluation of novel non-piperazine analogues of 1-[2-(diphenylmethoxy)ethyl]- and 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazines as dopamine transporter inhibitors.

A series of novel diamine, amine-amide, and piperazinone analogues of N-[2-(bisarylmethoxy)ethyl]-N'-(phenylpropyl)piperazines, GBR 12909 and 12935, were synthesized and evaluated as inhibitors of presynaptic monoamine neurotransmitter transporters. The primary objective of the study was to determine the structural requirements for selectivity of ligand binding and potency for neurotransmitter reuptake inhibition. In general, the target compounds retained transporter affinity; however, structural variations produced significant effects on reuptake inhibition and transporter selectivity. For example, analogues prepared by replacing the piperazine ring in the GBR structure with an N, N'-dimethylpropyldiamine moiety displayed enhanced selectivity for binding and reuptake inhibition at the norepinephrine (NE) transporter site (e.g. 4 and 5). Congeners in which the amide nitrogen atom was attached to the aralkyl moiety of the GBR molecule showed moderate affinity (K(i) = 51-61 nM) and selectivity for the dopamine transporter (DAT) site. In contrast, introduction of a carbonyl group adjacent to either nitrogen atom of the piperazine ring (e.g. 25 and 27) was not well tolerated. From the compounds prepared, analogue 16 was selected for further evaluation. With this congener, locomotor activity induced by cocaine at a dose of 20 mg/kg was attenuated with an AD(50) (dose attenuating cocaine-induced stimulation by 50%) of 60.0 +/- 3.6 mg/kg.     

Effects of neuronal and inducible NOS inhibitor 1-[2-(trifluoromethyl) phenyl] imidazole (TRIM) in unpredictable chronic mild stress procedure in mice

Nitric oxide is an intracellular messenger which is involved in several functions and pathologies such as depression, anxiety, learning and memory. In many studies nitric oxide synthase inhibitors (NOSI) were shown to possess antidepressant-like effects in animal models of depression. The aim of this study is to investigate the effects of a selective neuronal and inducible nitric oxide synthase inhibitor TRIM (30 mg/kg/day, 35 days) in mice subjected to unpredictable chronic mild stress and then compare it's effect with a conventional selective serotonin reuptake inhibitor fluoxetine (15 mg/kg/day, 35 days). Stressed vehicle animals showed a significant disturbed coat state when compared with nonstressed animals and this effect was reversed by TRIM or fluoxetine. Both TRIM and fluoxetine prevented the stress-induced deficit in the grooming behaviour in the splash test. TRIM and fluoxetine also significantly decreased the attack frequency when compared to the stressed control group in the resident-intruder test. These results support the assumption that NOS inhibitors can be a new class of antidepressant drugs possibly acting on neuronal NOS.     

Comparison of prediction methods for in vivo clearance of (S,S)-3-[3-(methylsulfonyl)phenyl]-1-propylpiperidine hydrochloride, a dopamine D2 receptor antagonist, in humans.

The purpose of this study is to investigate reliable prediction methods for in vivo pharmacokinetics and the likelihood of drug interactions with several cytochrome P450 inhibitors in humans for (S,S)-3-[3-(methylsulfonyl)phenyl]-1-propylpiperidine (PNU-96391). By allometric scaling of in vivo animal data, clearance of PNU-96391 in humans was over-predicted by 4-fold, half-life was under-predicted by 3-fold, and volume of distribution was accurately predicted. High correlation coefficients (>0.99) were observed for these parameters. Neither the in vitro-in vivo correlation approach nor the modified allometric scaling with maximum life span potential or brain weight accurately provided the predicted clearance value. Using an alternative method, based on normalization of in vitro human data with the ratio of in vivo to in vitro animal data, the in vivo clearance in humans was predicted to be 0.39 l/h/kg. This value correlated well with the in vivo value (0.43 l/h/kg). Regarding the interactions of PNU-96391 with cytochrome P450 inhibitors, only quinidine, haloperidol, and ketoconazole showed significant inhibition on the metabolic clearance of PNU-96391 in human hepatocytes. By comparing in vitro K(i) values with in vivo maximum unbound concentrations of the inhibitor, the increases in systemic exposure of PNU-96391 by coadministration of the inhibitors were estimated to be less than 1.5-fold. A preliminary comparison of pharmacokinetics of PNU-96391 between CYP2D6 extensive and poor metabolizers in the clinical study showed only a slight increase in systemic exposure in poor metabolizers (approximately 1.4-fold as area under the concentration-time curve). Therefore, clinically significant drug-drug interactions of PNU-96391 would be unlikely to occur with coadministration of CYP2D6 inhibitors.     

Labeling of dopamine transporter transmembrane domain 1 with the tropane ligand N-[4-(4-azido-3-[125I]iodophenyl)butyl]-2beta-carbomethoxy-3beta-(4-chlorophenyl)tropane implicates proximity of cocaine and substrate active sites

The novel photoaffinity ligand N-[4-(4-azido-3-(125)I-iodophenyl)-butyl]-2-beta-carbomethoxy-3beta-(4-chlorophenyl) tropane ([(125)I]MFZ 2-24) was used to investigate the site for cocaine binding on the dopamine transporter (DAT). [(125)I]MFZ 2-24 irreversibly labeled both rat striatal and expressed human DAT with high affinity and appropriate pharmacological specificity. Tryptic proteolysis of [(125)I]MFZ 2-24 labeled DAT followed by epitope-specific immunoprecipitation demonstrated that the ligand becomes adducted almost exclusively to transmembrane domains (TMs) 1-2. Further localization of [(125)I]MFZ 2-24 incorporation achieved by proteolyzing labeled wild-type and methionine mutant DATs with cyanogen bromide identified the sequence between residues 68 and 80 in TM1 as the ligand adduction site. This is in marked contrast to the previously identified attachment of the photoaffinity label [(125)I]RTI 82 in TM6. Because [(125)I]MFZ 2-24 and [(125)I]RTI 82 possess identical tropane pharmacophores and differ only in the placement of the reactive azido moieties, their distinct incorporation profiles identify the regions of the protein adjacent to different aspects of the cocaine molecule. These findings thus strongly support the direct interaction of cocaine on DAT with TM1 and TM6, both of which have been implicated by mutagenesis and homology to a bacterial leucine transporter as active sites for substrates. These results directly establish the proximity of TMs 1 and 6 in DAT and suggest that the mechanism of transport inhibition by cocaine involves close interactions with multiple regions of the substrate permeation pathway.     

Synthesis,radiosynthesis and in vivo evaluation of [123I]‐4‐(2‐(bis(4‐fluorophenyl)methoxy)ethyl)‐1‐(4‐iodobenzyl)piperidine as a selective tracer for imaging the dopamine transporter

Dopamine transporter (DAT) neuroimaging is a useful tool in Parkinson's disease diagnosis, staging and follow‐up providing information on the integrity of the dopaminergic neurotransmitter system in vivo. 4‐(2‐(Bis(4‐fluorophenyl)methoxy)ethyl)‐1‐(4‐iodobenzyl)piperidine (7) has nanomolar affinity for DAT and better selectivity over the other monoamine transporters compared with the existing SPECT radioligands for DAT. The aim of this study was to synthesize and evaluate [¹²³I]‐7 as an in vivo tracer for DAT. The tributylstannyl precursor was synthesized with an overall yield of 25%. [¹²³I]‐7 was synthesized by electrophilic destannylation with a yield of 40±10%. Radiochemical purity appeared to be >98%, whereas specific activity was at least 667 GBq/µmol. Biodistribution studies in mice showed brain uptake of 0.96±0.53%ID/g at 30 s post injection (p.i.) and 0.26±0.02%ID/g at 3 h p.i. High blood activity was observed at all time points. Pretreatment with Cyclosporin A raised brain uptake indicating that [¹²³I]‐7 is transported by P‐glycoprotein (P‐gp) pumps. In rats, regional brain distribution of [¹²³I]‐7 was not in agreement with DAT distribution. These results indicate that [¹²³I]‐7 is not suitable for mapping DAT in vivo but could be a useful tracer for the P‐gp transporter. Copyright © 2009 John Wiley & Sons, Ltd.     

Design and synthesis of 2- and 3-substituted-3-phenylpropyl analogs of 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine and 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)piperazine: role of amino, fluoro, hydroxyl, methoxyl, methyl, methylene, and oxo substituents on affinity for the dopamine and serotonin transporters

Novel derivatives of 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (GBR 12909, 1) and 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)piperazine (GBR 12935, 2) with various substituents in positions C2 and C3 of the phenylpropyl side chain were synthesized and evaluated for their ability to bind to the dopamine transporter (DAT) and the serotonin transporter (SERT). In the C2 series, the substituent in the S-configuration, with a lone-pair of electrons, significantly enhanced the affinity for DAT, whereas the steric effect of the substituent was detrimental to DAT binding affinity. In the C3 series, neither the lone electron pair nor the steric effect of the substituent seemed to affect DAT binding affinity, while sp (2) hybridized substituents had a detrimental effect on affinity for DAT. In the series, the 2-fluoro-substituted (S)-10 had the highest DAT binding affinity and good DAT selectivity, while the 2-amino-substituted (R)-8 showed essentially the same affinity for DAT and SERT. The oxygenated 16 and 18 possessed the best selectivity for DAT.     

In vivo effects of LR5182, cis-3-(3,4-dichlorophenyl)-2-n,n-dimethylaminomethyl- bicyclo-[2,2,2]-octane hydrochloride, an inhibitor of uptake into dopamine and norepinephrine neurons.

cis-3-(3,4-Dichlorophenyl)-2-N,N-dimethylaminomethyl-bicyclo-[2,2,2]-octane hydrochloride, (LR5182) antagonized the depletion of heart norepinephrine by 6-hydroxydopamine but not the depletion of brain serotonin by p-chloroamphetamine in mice. Norepinephrine depletion was antagonized by LR5182 following α-methyl-m-tyrosine injection into rats both in the cerebral hemispheres and in the hypothalamus. The drug also antagonized dopamine depletion in the cerebral hemispheres but did not antagonize epinephrine depletion in the hypothalamus in these rats. The concentration of α-methyl-m-tyramine and of metaraminol in the cerebral hemispheres of rats was lowered by LR5182 after α-methyl-m-tyrosine injection; since these amine metabolites are taken up and retained by dopamine and norepinephrine neurons, respectively, this lowering is a further indication of the inhibition of uptake into dopamine and norepinephrine neurons by LR5182. The elevation of brain DOPAC (3,4-dihydroxyphenylacetic acid) was significantly enhanced by LR5182 following spiperone injection, an effect characteristic of a particular subclass of dopamine uptake inhibitors.     

The dopamine autoreceptor agonist, (+/-)-trans-1,3,4,4a5,10b-hexahydro-4-propyl-2H [1]benzopyrano [3,4-b] pyridin-9-ol hydrochloride (CGS 15855A), modulates striatal dopamine metabolism and prolactin release

The effects of apomorphine and the putative dopamine autoreceptor agonist, CGS 15855A, were evaluated in several functional assays that are modulated by pre- or post-synaptic D2 receptors. These included release of prolactin in vivo and in vitro from cultured lactotrophs; levels of dihydroxyphenylacetic acid (DOPAC) in the striatum; levels of acetylcholine (ACh); in the striatum and concentrations of cyclic guanosine monophosphate (cyclic GMP) in the cerebellum. The secretion of prolactin was inhibited by CGS 15855A in vitro and in vivo and which also decreased the levels of DOPAC in the striatum at doses 5-25 times less than those required to increase ACh in the striatum and levels of cGMP in the cerebellum. In contrast, apomorphine possessed a dose-ratio between 1.5 and 8.6 for these assay systems. These data suggest that CGS 15855A is a selective dopamine autoreceptor agonist which preferentially stimulates D2 receptors on lactotrophs and dopaminergic neurons as compared to D2 receptors on cholinergic interneurons in the striatum.     

Synthesis and pharmacological properties of N,N-dialkyl(dialkenyl)amides of 7-methyl-3-phenyl-1-[2-hydroxy-3-(4-phenyl-1-piperazinyl)propyl]-2,4-dioxo-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidine-5-carboxylic acid

Synthesis of N,N-dialkyl(dialkenyl)amides of 7-methyl-3-phenyl-2,4-dioxo-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidine-5-carboxylic acid (5-9) and their 1-[2-hydroxy-3-(4-phenyl-1-piperazinyl)propyl] derivatives (10-14) is described. Compounds 10-14 were tested for analgesic and sedative activities as well as for mu-opioid receptors binding affinities. All the amides, being the object of investigation, displayed an interesting analgesic action, which in case of the compounds 10-12 and 14 was superior to that of acetylsalicylic acid in two different tests. Furthermore all the amides (10-14) significantly suppressed the spontaneous locomotor activity, prolonged barbiturate sleep in mice and showed a weak affinity to mu-opioid receptors.     

Selective action of (-)-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate (LY379268), a group II metabotropic glutamate receptor agonist, on basal and phencyclidine-induced dopamine release in the nucleus accumbens shell

The effect of the group II metabotropic receptor agonist (-)-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate (LY379268), on basal and phencyclidine-induced dopamine efflux were measured in the shell and core subdivisions of the nucleus accumbens--regions which are associated with limbic and motor functions, respectively. Extracellular levels of dopamine were measured using microdialysis in conscious animals, and LY379268 was delivered locally by inclusion in the artificial cerebrospinal fluid (aCSF) flowing through the microdialysis probe. Local administration of LY379268 in the concentration range 10 nM-10 microM reduced basal levels of dopamine in the nucleus accumbens shell, whilst having no effect in the nucleus accumbens core. In the nucleus accumbens shell, basal levels were reduced to approximately 60% compared to the pre-injection control, with a maximal reduction occurring at concentrations of LY379268 > or =100 nM. The response to LY379268 (100 nM) was reversible, with levels returning to baseline following its removal from the aCSF. In a separate experiment, local perfusion of the nucleus accumbens shell with LY379268 (at both 1 and 10 microM) reduced the magnitude of the response to a subsequent systemic administration of phencyclidine (5 mg/kg i.p.). The reduction in the peak dopamine response was only evident with doses of LY379268 that also reduced basal dopamine efflux--LY379268 being ineffective against PCP at 10 nM. However, in animals pre-treated with LY379268 at 1 or 10 microM, PCP still evoked a dopamine response, and in these animals the relative extent of the response was not significantly different between the respective treatment groups. In contrast, in the nucleus accumbens core the magnitude of the dopamine response to PCP was unaffected by local application of LY379268 (at 1 or 10 microM). Our data suggest that within the nucleus accumbens, there exists a distinct regional difference in the control of dopamine release by group II mGluRs, with the nucleus accumbens shell being preferentially affected. Moreover, the selective action of LY379268 on dopamine levels in the nucleus accumbens shell may have implications for the potential antipsychotic activity of group II mGluR agonists.     

In vitro metabolism of 10-(3-chlorophenyl)-6,8,9,10-tetrahydrobenzo[b][1,8]naphthyridin-5(7H)-one,a topical antipsoriatic agent. Use of precision-cut rat,dog, monkey and human liver slices,and chemical synthesis of metabolites

The metabolism of SCH 40120, which is the clinically effective antipsoriatic drug 10-(3-chlorophenyl)-6,8,9,10-tetrahydrobenzol[b][1,8]naphthyridin-5(7H)-one, was determined in vitro. Rat, dog, cynomolgus monkey, and human liver slices hydroxylated the aliphatic, cyclohexenyl ring of the drug and conjugated the resulting carbinol. The identified metabolites comprised the corresponding 6-, 7-, and 9-carbinols, the glucuronide of the 6-carbinol, and the 6-ketone derived from the parent drug. Although the three carbinols appeared in the liver isolates of all species studied, the relative amounts of these metabolites varied across species. With a high, non-physiological ratio of substrate to liver, the 6-carbinol and its glucuronide were the major metabolites in human and monkey, whereas the 6-ketone was a minor metabolite in dog. Containing a stereogenic axis and center, the 6-carbinol existed as diastereomeric atropisomers. Its structure was established by ¹³C and ¹H NMR spectroscopy, mass spectrometry, and comparison to an authentic sample. © 1998 John Wiley & Sons, Ltd.     

Neurochemical and behavioural profile of Lu 17-133, (±)-trans-4-[3-(3,4-dichlorophenyl)-indan-1-yl]-1-piperazineethanol,an inhibitor of the uptake of dopamine and noradrenaline

The neurochemical and behavioural profile of Lu 17-133, (±)-trans-4-[3-(3,4-dichlorophenyl)-indan-1-yl]-1-piperazineethanol has been characterized and compared with that of a series of inhibitors of biogenic amine uptake. Lu 17-133 inhibits the uptake of dopamine and noradrenaline in the nanomolar range, but it has only a weak effect on serotonin uptake. Blockade of receptors for dopamine (D-1, D-2), noradrenaline (α₁, α₂), histamine (H₁), acetylcholine (muscarinic), and serotonin (5-HT₂) was absent or seen only at micromolar concentrations. The biochemical profile is close to that of GBR 13.069, GBR 12.921, and Lu 19-005 (INN name, Indatraline). Lu 17-133 shows only weak behavioural effects. In high doses, it potentiates apomorphine and 5-HTP and reverses the effect of tetrabenazine in mice. It has minimal stimulatory property, as it increases very weakly the locomotor activity in mice and does not induce stereotypy (either low-component or oral stereotypy) in rats. It does not induce ipsilateral circling behaviour in 6-OHDA-lesioned rats, although in combination with scopolamine, a full ipsilateral rotation is seen. Lu 17-133 has no anticataleptic effect and does not generalize to the discriminative stimulus properties induced by d-amphetamine. Experiments have shown that there is no clear correlation between inhibitory effect on dompamine uptake and in vivo effects in the models detecting dopamine-stimulating compounds; nor is there any obvious correlation between effects in different in vivo test models. The neurochemical and behavioural characteristics of Lu 17-133-inhibition of dopamine- and noradrenaline-uptake in vitro with low stimulatory properties in vivo make it an interesting candidate as a new antidepressant drug.     

SB-616234-A (1-[6-(cis-3,5-dimethylpiperazin-1-yl)-2,3-dihydro-5-methoxyindol-1-yl]-1-[2'methyl-4'-(5-methyl-1,2,3-oxadiazol-3-yl)biphenyl-4-yl]methanone hydrochloride): a novel, potent and selective 5-HT1B receptor antagonist

SB-616234-A possesses high affinity for human 5-HT_1B receptors stably expressed in Chinese hamster ovary (CHO) cells (pK_i 8.3 ± 0.2), and is over 100-fold selective for a range of molecular targets except h5-HT_1D receptors (pK_i 6.6 ± 0.1). Similarly, affinity (pK_i) for rat and guinea pig striatal 5-HT_1B receptors is 9.2 ± 0.1. In [³⁵S]-GTPγS binding studies in the human recombinant cell line, SB-616234-A acted as a high affinity antagonist with a pA₂ value of 8.6 ± 0.2 whilst providing no evidence of agonist activity in this system. In [³⁵S]-GTPγS binding studies in rat striatal membranes, SB-616234-A acted as a high affinity antagonist with an apparent pK_B of 8.4 ± 0.5, again whilst providing no evidence of agonist activity in this system. SB-616234-A (1 μM) potentiated electrically stimulated [³H]-5-HT release from guinea pig and rat cortical slices (S₂/S₁ ratios of 1.8 and 1.6, respectively). SB-616234-A (0.3–30 mg kg⁻¹ p.o.) caused a dose-dependent inhibition of ex vivo [³H]-GR125743 binding to rat striatal 5-HT_1B receptors with an ED₅₀ of 2.83 ± 0.39 mg kg⁻¹ p.o. Taken together these data suggest that SB-616234-A is a potent and selective 5-HT_1B autoreceptor antagonist that occupies central 5-HT_1B receptors in vivo following oral administration.     

A Search for New 5-HT1A/5-HT2A Receptor Ligands. In Vitro and in vivo Studies of 1-[ω-(4-Aryl-1-piperazinyl)alkyl]indolin-2(1H)-ones

A series of 1-[ω-(4-aryl-1-piperazinyl)alkyl]indolin-2(1H)-one derivatives 2–14 was synthesized in order to obtain ligands with a dual 5-HT_1A/5-HT_2A activity. The majority of those compounds ( 2–5, 7, 10–13 ) exhibited a high 5-HT_1A (K_i = 2 – 44 nM) and/or 5-HT_2A affinity (K_i = 51 and 39 for 5 and 7 , respectively). Induction of lower lip retraction (LLR) and behavioral syndrome and inhibition of these efects evoked by 8-hydroxy-2-(di-n-propyl-amino)tetralin (8-OH-DPAT) were used for determination the agonistic and antagonistic activity, respectively, at 5-HT_1A receptors. The 5-HT_2A antagonistic activity was assessed by the blocking effect on the head twitches induced by (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in mice. Two of the tested compounds, 1-{3-[4-(3-chlorophenyl)-1-piperazinyl]propyl}-6-fluoroindolin-2(1H)-one ( 5 ) and 1-{3-[4-(2-methoxyphenyl)-1-piperazinyl]propyl}indolin-2(1H)-one ( 7 ), demonstrated a high 5-HT_1A/5-HT_2A affinity and an in vivo antagonistic activity towards both receptor subtypes.     

Characterisation of the selective 5-HT1B receptor antagonist SB-616234-A (1-[6-(cis-3,5-dimethylpiperazin-1-yl)-2,3-dihydro-5-methoxyindol-1-yl]-1-[2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)biphenyl-4-yl]methanone hydrochloride): in vivo neurochemical and behavioural evidence of anxiolytic/antidepressant activity

The 5-HT_1B receptor has attracted significant interest as a potential target for the development of therapeutics for the treatment of affective disorders such as anxiety and depression. Here we present the in vivo characterisation of a novel, selective and orally bioavailable 5-HT_1B receptor antagonist, SB-616234-A (1-[6-(cis-3,5-dimethylpiperazin-1-yl)-2,3-dihydro-5-methoxyindol-1-yl]-1-[2′-methyl-4′-(5-methyl-1,2,4-oxadiazol-3-yl)biphenyl-4-yl]methanone hydrochloride). SB-616234-A reversed the 5-HT_1/7 receptor agonist, SKF-99101H-induced hypothermia in guinea pigs in a dose related manner with an ED₅₀ of 2.4 mg/kg p.o. Using in vivo microdialysis in freely moving guinea pigs, SB-616234-A (3–30 mg/kg p.o.) caused a dose-related increase in extracellular 5-HT in the dentate gyrus. Evaluation of antidepressant- and anxiolytic-like effects of this 5-HT_1B receptor antagonist was performed in a variety of models and species. SB-616234-A produced a decrease in immobility time in the mouse forced swim test; an effect suggestive of antidepressant activity. Furthermore, SB-616234-A produced dose-related anxiolytic effects in both rat and guinea pig maternal separation-induced vocalisation models with an ED₅₀ of 1.0 and 3.3 mg/kg i.p., respectively (vs fluoxetine treatment ED₅₀ = 2.2 mg/kg i.p. in both species). Also a significant reduction in posturing behaviours was observed in the human threat test in marmosets; an effect indicative of anxiolytic activity. In summary, SB-616234-A is a novel, potent and orally bioavailable 5-HT_1B receptor antagonist which exhibits a neurochemical and behavioural profile that is consistent with both anxiolytic- and antidepressant-like activity in a variety of species. Taken together these data suggest that SB-616234-A may have therapeutic efficacy in the treatment of affective disorders.