Effects of N-phenylpropyl-N′-substituted piperazine sigma receptor ligands on cocaine-induced hyperactivity in mice

Sigma-1 receptors (σ1Rs) are structurally unique intracellular proteins that function as chaperones. σ1Rs translocate from the mitochondria-associated membrane to other sub-cellular compartments, and can influence a host of targets, including ion channels, G-protein-coupled receptors, lipids, and other signaling proteins. Drugs binding to σRs can induce or block the actions of σRs. Studies indicate that stimulant self-administration induces reinforcing effects of σR agonists, due to dopamine transporter actions. Once established the reinforcing effects of σR agonists are independent of dopaminergic mechanisms traditionally thought to be critical in the reinforcing effects of stimulants. Self-administered doses of σR agonists do not increase dopamine concentrations in the nucleus accumbens shell, a transmitter and brain region considered important for reinforcing effects of abused drugs. However, the self-administration of σR agonists is blocked by σR antagonists. Several effects of stimulants have been blocked by σR antagonists, including reinforcing effects assessed by a place-conditioning procedure. However, the self-administration of stimulants is largely unaffected by σR antagonists, indicating fundamental differences in the mechanisms underlying these two procedures used to assess reinforcing effects. When σR antagonists are administered in combination with dopamine uptake inhibitors an effective and specific blockade of stimulant self-administration is obtained. Actions of stimulant drugs related to their abuse induce unique changes in σR activity and the changes induced potentially create redundant, and once established, independent reinforcement pathways. Concomitant targeting of both dopaminergic pathways and σR proteins produces a selective antagonism of stimulant self-administration, suggesting new avenues for combination chemotherapies to specifically combat stimulant abuse.

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“…Several other studies replicated these outcomes (e.g. Sage et al, 2013, Mori et al, 2012; Mori et al, 2014). …”

Section: σR Ligands and Reinforcing Effects Of Stimulant Drugsmentioning

confidence: 65%

A role for sigma receptors in stimulant self-administration and addiction

Katz

Hong²,

Hiranita³

et al. 2016

Behavioural Pharmacology

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“…Effects of PD144418 on basal locomotor activity and cocaine-induced locomotor stimulation in mice were evaluated by procedures similar to those used previously for evaluations of other s receptor ligands (Rodvelt et al, 2011;Sage et al, 2013). Experiments were performed in activity monitors (Model ENV-515; Med Associates Inc., Georgia, VT) consisting of a transparent box surrounded by banks of infrared sensors that were connected to a computer.…”

Section: Methodsmentioning

confidence: 99%

Relationship between Cerebral Sigma-1 Receptor Occupancy and Attenuation of Cocaine’s Motor Stimulatory Effects in Mice by PD144418

Lever

Miller

Fergason-Cantrell

et al. 2014

J Pharmacol Exp Ther

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Psychostimulant effects of cocaine are mediated partly by agonist actions at sigma-1 (s 1 ) receptors. Selective s 1 receptor antagonists attenuate these effects and provide a potential avenue for pharmacotherapy. However, the selective and high affinity s 1 antagonist PD144418 (1,2,3,6-tetrahydro-5-[3-(4-methylphenyl)-5-isoxazolyl]-1-propylpyridine) has been reported not to inhibit cocaine-induced hyperactivity. To address this apparent paradox, we evaluated aspects of PD144418 binding in vitro, investigated s 1 receptor and dopamine transporter (DAT) occupancy in vivo, and re-examined effects on locomotor activity. PD144418 displayed high affinity for s 1 sites (K i 0.46 nM) and 3596-fold selectivity over s 2 sites (K i 1654 nM) in guinea pig brain membranes. No appreciable affinity was noted for serotonin and norepinephrine transporters (K i .100 mM), and the DAT interaction was weak (K i 9.0 mM). In vivo, PD144418 bound to central and peripheral s 1 sites in mouse, with an ED 50 of 0.22 mmol/kg in whole brain. No DAT occupancy by PD144418 (10.0 mmol/kg) or possible metabolites were observed. At doses that did not affect basal locomotor activity, PD144418 (1, 3.16, and 10 mmol/kg) attenuated cocaine-induced hyperactivity in a dosedependent manner in mice. There was good correlation (r 2 5 0.88) of hyperactivity reduction with increasing cerebral s 1 receptor occupancy. The behavioral ED 50 of 0.79 mmol/kg corresponded to 80% occupancy. Significant s 1 receptor occupancy and the ability to mitigate cocaine's motor stimulatory effects were observed for 16 hours after a single 10.0 mmol/kg dose of PD144418.

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“…Non-radioactive E -IA-DM-PE-PIPZE also partially attenuates (−)-cocaine induced locomotor hyperactivity, suggesting antagonist character [58]. At present, such behavioral studies are a principal way to assign the functional properties of σ 1 receptor ligands [38,64,179,180]. Dopamine transporter (DAT) inhibition is recognized as the main contributor to (−)-cocaine’s behavioral effects and abuse liability.…”

Section: Preclinical Imagingmentioning

confidence: 99%

Tactics for preclinical validation of receptor-binding radiotracers

Lever

Fan

Lever

2017

Nuclear Medicine and Biology

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Introduction Aspects of radiopharmaceutical development are illustrated through preclinical studies of [125I]-(E)-1-(2-(2,3-dihydrobenzofuran-5-yl)ethyl)-4-(iodoallyl)piperazine ([125I]-E-IA- BF-PE-PIPZE), a radioligand for sigma-1 (σ1) receptors, coupled with examples from the recent literature. Findings are compared to those previously observed for [125I]-(E)-1-(2-(2,3-dimethoxy-5-yl)ethyl)-4-(iodoallyl)piperazine ([125I]-E-IA-DM-PE-PIPZE). Methods Syntheses of E-IA-BF-PE-PIPZE and [125I]-E-IA-BF-PE-PIPZE were accomplished by standard methods. In vitro receptor binding studies and autoradiography were performed, and binding potential was predicted. Measurements of lipophilicity and protein binding were obtained. In vivo studies were conducted in mice to evaluate radioligand stability, as well as specific binding to σ1 sites in brain, brain regions and peripheral organs in the presence and absence of potential blockers. Results E-IA-BF-PE-PIPZE exhibited high affinity and selectivity for σ1 receptors (Ki = 0.43 ± 0.03 nM, σ2 / σ1 = 173). [125I]-E-IA-BF-PE-PIPZE was prepared in good yield and purity, with high specific activity. Radioligand binding provided dissociation (koff) and association (kon) rate constants, along with a measured Kd of 0.24 ± 0.01 nM and Bmax of 472 ± 13 fmol / mg protein. The radioligand proved suitable for quantitative autoradiography in vitro using brain sections. Moderate lipophilicity, Log D7.4 2.69 ± 0.28, was determined, and protein binding was 71 ± 0.3%. In vivo, high initial whole brain uptake, > 6% injected dose / g, cleared slowly over 24 h. Specific binding represented 75% to 93% of total binding from 15 min to 24 h. Findings were confirmed and extended by regional brain biodistribution. Radiometabolites were not observed in brain (1%). Conclusions Substitution of dihydrobenzofuranylethyl for dimethoxyphenethyl increased radioligand affinity for σ1 receptors by 16-fold. While high specific binding to σ1 receptors was observed for both radioligands in vivo, [125I]-E-IA-BF-PE-PIPZE displayed much slower clearance kinetics than [125I]-E-IA-DM-PE-PIPZE. Thus, minor structural modifications of σ1 receptor radioligands lead to major differences in binding properties in vitro and in vivo.

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Effects of N-phenylpropyl-N′-substituted piperazine sigma receptor ligands on cocaine-induced hyperactivity in mice

Cited by 11 publications

References 26 publications

A role for sigma receptors in stimulant self-administration and addiction

A role for sigma receptors in stimulant self-administration and addiction

Relationship between Cerebral Sigma-1 Receptor Occupancy and Attenuation of Cocaine’s Motor Stimulatory Effects in Mice by PD144418

Tactics for preclinical validation of receptor-binding radiotracers

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