BackgroundThe noradrenergic system contributes to pain modulation, but the roles of its specific adrenoceptors are still being defined. We have identified a novel, potent (rat EC50=4.3nM) and selective (2B) receptor agonist, A-1262543, to further explore this adrenoceptor subtype's contribution to pathological nociception.MethodsSystemic administration of A-1262543 (1-10mg/kg, intraperitoneal) dose-dependently attenuated mechanical allodynia in animals with a spinal nerve ligation injury. To further explore its mechanism of action, the activity of nociceptive neurones in the spinal cord and medial prefrontal cortex (mPFC) were examined after injection of 3mg/kg of A-1262543 (intravenous, i.v.). These effects were compared with duloxetine (3mg/kg, i.v.), a dual noradrenaline (NA) and serotonin (5-HT) reuptake inhibitor.ResultsSystemic administration of A-1262543 or duloxetine did not alter the spontaneous or evoked firing of spinal wide dynamic range and nociceptive-specific neurones in the neuropathic rats, indicating that neither compound engaged spinal, peripheral or descending pathways. In contrast to the lack of effect on spinal neurones, both A-1262543 and duloxetine reduced the evoked and spontaneous firing of pain-responsive' (PR) neurones in the mPFC. Duloxetine, but not A-1262543, also inhibited the firing of pain non-responsive (nPR) neurones in the mPFC probably reflecting duloxetine's contribution to modulating non-pain endpoints.ConclusionsThese data highlight that activation of the (2B) adrenoceptor as well as inhibiting NA and 5-HT reuptake can result in modulating the ascending nociceptive system, and in particular, dampening the firing of PR neurones in the mPFC.

We investigated the systemic and site-specific actions of a selective CB(2) receptor agonist, A-836339 on mechanically evoked (10 g von Frey hair) and spontaneous firing of spinal wide dynamic range (WDR) neurons in neuropathic (L5 and L6 ligations) and sham rats. Systemic administration of A-836339 (0.3-3 micromol/kg, i.v.) reduced both evoked and spontaneous WDR neuronal activity in neuropathic, but not sham rats. The effects in neuropathic rats were blocked by pre-administration of a CB(2), but not a CB(1), receptor antagonist. Similar to systemic delivery, intra-spinal injection of A-836339 (0.3 and 1 nmol) also attenuated both von Frey-evoked and spontaneous firing of WDR neurons in neuropathic rats. Intra-spinal injections of A-836339 were ineffective in sham rats. Application of A-836339 (3-30 nmol) onto the ipsilateral L5 dorsal root ganglion (DRG) of neuropathic rats reduced the von Frey-evoked activity of WDR neurons, but spontaneous firing was unaltered. All effects of A-836339 on WDR neuronal activity following either intra-spinal or intra-DRG administration were blocked by pre-administration of a CB(2) receptor antagonist. Pre-administration of a CB(1) receptor antagonist did not alter the site-specific effects of A-836339. Injection of A-836339 (300 nmol) into the neuronal receptive field on the ipsilateral hind paw did not affect evoked or spontaneous firing of WDR neurons. Thus, the current data demonstrate that modulation of spinal neuronal activity by a CB(2) receptor agonist is enhanced following peripheral nerve injury, and further delineate the contribution of spinal and peripheral CB(2) receptors to this modulation.

Background and purpose: Activation of cannabinoid (CB) receptors decreases nociceptive transmission in inflammatory or neuropathic pain states. However, the effects of CB receptor agonists in post‐operative pain remain to be investigated. Here, we characterized the anti‐allodynic effects of WIN 55,212‐2 (WIN) in a rat model of post‐operative pain. Experimental approach: WIN 55,212‐2 was characterized in radioligand binding and in vitro functional assays at rat and human CB 1 and CB 2 receptors. Analgesic activity and site(s) of action of WIN were assessed in the skin incision‐induced post‐operative pain model in rats; receptor specificity was investigated using selective CB 1 and CB 2 receptor antagonists. Key results: WIN 55,212‐2 exhibited non‐selective affinity and agonist efficacy at human and rat CB 1 versus CB 2 receptors. Systemic administration of WIN decreased injury‐induced mechanical allodynia and these effects were reversed by pretreatment with a CB 1 receptor antagonist, but not with a CB 2 receptor antagonist, given by systemic, intrathecal and supraspinal routes. In addition, peripheral administration of both CB 1 and CB 2 antagonists blocked systemic WIN‐induced analgesic activity. Conclusions and implications: Both CB 1 and CB 2 receptors were involved in the peripheral anti‐allodynic effect of systemic WIN in a pre‐clinical model of post‐operative pain. In contrast, the centrally mediated anti‐allodynic activity of systemic WIN is mostly due to the activation of CB 1 but not CB 2 receptors at both the spinal cord and brain levels. However, the increased potency of WIN following i.c.v. administration suggests that its main site of action is at CB 1 receptors in the brain. British Journal of Pharmacology (2009) 157, 645–655; doi:10.1111/j.1476‐5381.2009.00184.x; published online 3 April 2009

Background and purpose: The alpha 7 nicotinic acetylcholine receptor ( nAChR) has attracted considerable interest as a target for cognitive enhancement in schizophrenia and Alzheimer's Disease. However, most recently described alpha 7 agonists are derived from the quinuclidine structural class. Alternatively, the present study identifies tilorone as a novel alpha 7-selective agonist and characterizes analogues developed from this lead.Experimental approach: Activity and selectivity were determined from rat brain alpha 7 and alpha 4 beta 2 nAChR binding, recombinant nAChR activation, and native alpha 7 nAChR mediated stimulation of ERK1/2 phosphorylation in PC12 cells.Key results: Tilorone bound alpha 7 nAChR (IC50 110 nM) with high selectivity relative to alpha 4 beta 2 ( IC50 70 000 nM), activated human alpha 7 nAChR with an EC50 value of 2.5 mu M and maximal response of 67% relative to acetylcholine, and showed little agonist effect at human alpha 3 beta 4 or alpha 4 beta 2 nAChRs. However, the rat alpha 7 nAChR maximal response was only 34%. Lead optimization led to 2-(5-methyl-hexahydro-pyrrolo[3,4-c]pyrrol-2-yl)-xanthen-9-one(A-844606) with improved binding (alpha 7 IC50 11 nM, alpha 4 beta 2 IC50 > 30000 nM) and activity at both human and rat alpha 7 nAChR (EC(50)s 1.4 and 2.2 mu M and apparent efficacies 61 and 63%, respectively). These compounds also activated native alpha 7 nAChR, stimulating ERK1/2 phosphorylation in PC12 cells.Conclusions and implications: Tilorone, known as an interferon inducer, is a selective alpha 7 nAChR agonist, suggesting utility of the fluorenone pharmacophore for the development of alpha 7 nAChR selective agonists. Whether alpha 7 stimulation mediates interferon induction, or whether interferon induction may influence the potential anti-inflammatory properties of alpha 7 nAChR agonists remains to be elucidated.

Background and purpose: Activation of cannabinoid CB1 and/or CB2 receptors mediates analgesic effects across a broad spectrum of preclinical pain models. Selective activation of CB2 receptors may produce analgesia without the undesirable psychotropic side effects associated with modulation of CB1 receptors. To address selectivity in vivo, we describe non-invasive, non-ionizing, functional data that distinguish CB1 from CB2 receptor neural activity using pharmacological MRI (phMRI) in awake rats.Experimental approach: Using a high field (7 T) MRI scanner, we examined and quantified the effects of non-selective CB1/CB2 (A-834735) and selective CB2 (AM1241) agonists on neural activity in awake rats. Pharmacological specificity was determined using selective CB1 (rimonabant) or CB2 (AM630) antagonists. Behavioural studies, plasma and brain exposures were used as benchmarks for activity in vivo.Key results: The non-selective CB1/CB2 agonist produced a dose-related, region-specific activation of brain structures that agrees well with published autoradiographic CB1 receptor density binding maps. Pretreatment with a CB1 antagonist but not with a CB2 antagonist, abolished these activation patterns, suggesting an effect mediated by CB1 receptors alone. In contrast, no significant changes in brain activity were found with relevant doses of the CB2 selective agonist.Conclusion and implications: These results provide the first clear evidence for quantifying in vivo functional selectivity between CB1 and CB2 receptors using phMRI. Further, as the presence of CB2 receptors in the brain remains controversial, our data suggest that if CB2 receptors are expressed, they are not functional under normal physiological conditions.

Background and purpose: Selective cannabinoid CB 2 receptor agonists have demonstrated analgesic activity across multiple preclinical pain models. AM1241 is an indole derivative that exhibits high affinity and selectivity for the CB 2 binding site and broad spectrum analgesic activity in rodent models, but is not an antagonist of CB 2 in vitro functional assays. Additionally, its analgesic effects are μ‐opioid receptor‐dependent. Herein, we describe the in vitro and in vivo pharmacological properties of A‐796260, a novel CB 2 agonist. Experimental approach: A‐796260 was characterized in radioligand binding and in vitro functional assays at rat and human CB 1 and CB 2 receptors. The behavioural profile of A‐796260 was assessed in models of inflammatory, post‐operative, neuropathic, and osteoarthritic (OA) pain, as well as its effects on motor activity. The receptor specificity was confirmed using selective CB 1 , CB 2 and μ‐opioid receptor antagonists. Key results: A‐796260 exhibited high affinity and agonist efficacy at human and rat CB 2 receptors, and was selective for the CB 2 vs CB 1 subtype. Efficacy in models of inflammatory, post‐operative, neuropathic and OA pain was demonstrated, and these activities were selectively blocked by CB 2 , but not CB 1 or μ‐opioid receptor‐selective antagonists. Efficacy was achieved at doses that had no significant effects on motor activity. Conclusions and implications: These results further confirm the therapeutic potential of CB 2 receptor‐selective agonists for the treatment of pain. In addition, they demonstrate that A‐796260 may be a useful new pharmacological compound for further studying CB 2 receptor pharmacology and for evaluating its role in the modulation of pain. British Journal of Pharmacology (2008) 153 , 390–401; doi: 10.1038/sj.bjp.0707568 ; published online 12 November 2007

BACKGROUND AND PURPOSE:The CB2 receptor has been proposed as a novel target for the treatment of pain, and CB2 receptor agonists defined in in vitro assays have demonstrated analgesic activity in animal models. Based on its in vivo analgesic efficacy, AM1241 has been classified as a CB2-selective agonist. However, in vitro characterization of AM1241 in functional assays has not been reported.EXPERIMENTAL APPROACH:In this study, AM1241 was characterized across multiple in vitro assays employing heterologous recombinant receptor expression systems to assess its binding potencies at the human CB2 and CB1 receptors and its functional efficacies at the human CB2 receptor.KEY RESULTS:AM1241 exhibited distinct functional properties depending on the assay conditions employed, a unique profile in contrast to those of the agonist CP 55,940 and the inverse agonist SR144528. AM1241 displayed neutral antagonist activities in FLIPR and cyclase assays. However, when cyclase assays were performed using lower forskolin concentrations for stimulation, AM1241 exhibited partial agonist efficacy. In addition, it behaved as a partial agonist in ERK (or MAP) kinase assays.CONCLUSIONS AND IMPLICATIONS:The unusual phenomenon of inconsistent functional efficacies suggests that AM1241 is a protean agonist at the CB2 receptor. We postulate that functional efficacies displayed by protean agonists in various assay systems may depend on the levels of receptor constitutive activities exhibited in the assay systems, and therefore, efficacies observed in in vitro assays may not predict in vivo activities.

The synthesis and in vitro characterization of A-119637 and A-123189, two novel, selective and potent alpha1D antagonists, are described.

Pharmacological activation of neuronal nicotinic acetylcholine receptors can produce non-opioid antinociception in rodents. However, multiple nAChR subtypes exist, the most abundant of which contain alpha4 and beta2 subunits. The purpose of the present study was to investigate the role of alpha4-containing nAChRs in mediating nicotinic antinociception using an in vivo antisense strategy. Both i.c.v. infusion and repeated bolus injections into the cerebral aqueduct of an antisense oligonucleotide against the alpha4 subunit significantly attenuated the antinociceptive effects of the nAChR agonist A-85380 in the paw withdrawal test of acute thermal pain. Rats treated with a scrambled oligonucleotide displayed a full antinociceptive response to A-85380, while discontinuing antisense treatment restored the antinociceptive effects of the nicotinic agonist. Double immunohistochemical labeling revealed near-complete overlap of expression of the serotonin marker tryptophan hydroxylase and the alpha4 nAChR subunit in the dorsal raphe nucleus. The expression of alpha4-containing nAChRs by serotonergic neurons in the dorsal raphe offered a means to address nonspecific alpha4 knock-down, i.e., oligonucleotide-induced neurotoxicity. Immunohistochemical detection of alpha4 expression was reduced by nearly 50% in the dorsal raphe of antisense-treated rats as compared to either saline or missense-treated controls. In contrast, the expression of tryptophan hydroxylase, as well as, the alpha7 nAChR subunit in antisense-infused rats was similar to that observed in saline- and missense-treated controls. The results of these studies suggest that alpha4-containing nAChRs, possibly expressed by serotonergic neurons, are involved in nicotinic-mediated analgesia. However, these data do not eliminate the possibility that other nicotinic subunit combinations may also play a role in antinociception produced by nAChR activation.

In search of an alpha2-antagonist/5-HT uptake inhibitor as a potential new class of antidepressant with a more rapid onset of action, compound 3 was prepared and observed to possess high affinity for the alpha2-receptor (K(i) = 6.71 nM) and the 5-HT uptake site (20.6 nM). A series of tertiary amine analogs of 3 were synthesized and assayed for their affinity at both the alpha2-receptor and the 5-HT uptake site. The structure-activity relationship reveals that a variety of structural modifications to the arylethyl fragment are possible with retention of this dual activity. On the tetralin portion, 5-OMe substitution and the (R) stereochemistry at C-1 are optimal with alternate substitutions producing compounds retaining high affinity for the alpha2-receptor but lacking affinity for the 5-HT uptake site. Data for several rigidified 5-O-alkyl analogs suggests that the favored orientation of the oxygen lone pairs may be away from the 6-position of the tetralin.

ADVERTISEMENT RETURN TO ISSUELetterNEXTSynthesis and Pharmacological Characterization of 3-[2-((3aR,9bR)-cis-6-Methoxy- 2,3,3a,4,5,9b-hexahydro-1H- benz[e]isoindol-2-yl)ethyl]pyrido[3',4':4,5]thieno[3,2-d]pyrimidine- 2,4(1H,3H)-dione (A-131701): A Uroselective α1A Adrenoceptor Antagonist for the Symptomatic Treatment of Benign Prostatic Hyperplasia 1Michael D. Meyer, Robert J. Altenbach, Fatima Z. Basha, William A. Carroll, Irene Drizin, Steven W. Elmore, Paul P. Ehrlich, Suzanne A. Lebold, Karin Tietje, Kevin B. Sippy, Michael D. Wendt, Daniel J. Plata, Fred Plagge, Steven A. Buckner, Michael E. Brune, Arthur A. Hancock, and James F. KerwinView Author Information Neurological and Urological Diseases Research, D-47C, and Process Research, D-45L, Abbott Laboratories, Abbott Park, Illinois 60064-3500 Cite this: J. Med. Chem. 1997, 40, 20, 3141–3143Publication Date (Web):September 26, 1997Publication History Received2 June 1997Published online26 September 1997Published inissue 1 September 1997https://pubs.acs.org/doi/10.1021/jm970364ahttps://doi.org/10.1021/jm970364arapid-communicationACS PublicationsCopyright © 1997 American Chemical SocietyRequest reuse permissionsArticle Views508Altmetric-Citations16LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Amines,Anatomy,Antagonists,Receptors,Selectivity Get e-Alerts

The existence of multiple subtypes of the alpha 1 adrenergic receptor has been demonstrated both pharmacologically and by molecular biological cloning techniques. The development of subtype selective antagonists has been the focus of much research within the pharmaceutical industry, and clinical evidence now exists that alpha-1A selective antagonists will have utility in the treatment of benign prostatic hyperplasia. However, highly subtype selective agonists are not known. Herein we report the synthesis and pharmacological characterization of N-[5-(4,5-dihydro-1H-imidazol-2-yl)-2-hydroxy-5,6,7,8- tetrahydronaphthalen-1-yl]methanesulfonamide and its enantiomers, a highly potent full agonist with excellent selectivity for the alpha 1A receptor subtype.