Concept: Adrenergic receptor
Transcranical direct current stimulation (tDCS) is a treatment known to ameliorate various neurological conditions and enhance memory and cognition in humans. tDCS has gained traction for its potential therapeutic value; however, little is known about its mechanism of action. Using a transgenic mouse expressing G-CaMP7 in astrocytes and a subpopulation of excitatory neurons, we find that tDCS induces large-amplitude astrocytic Ca(2+) surges across the entire cortex with no obvious changes in the local field potential. Moreover, sensory evoked cortical responses are enhanced after tDCS. These enhancements are dependent on the alpha-1 adrenergic receptor and are not observed in IP3R2 (inositol trisphosphate receptor type 2) knockout mice, in which astrocytic Ca(2+) surges are absent. Together, we propose that tDCS changes the metaplasticity of the cortex through astrocytic Ca(2+)/IP3 signalling.
Impairments in metacognition, the ability to accurately report one’s performance, are common in patients with psychiatric disorders, where a putative neuromodulatory dysregulation provides the rationale for pharmacological interventions. Previously, we have shown how unexpected arousal modulates metacognition (Allen et al., 2016). Here, we report a double-blind, placebo-controlled, study that examined specific effects of noradrenaline and dopamine on both metacognition and perceptual decision making. Signal theoretic analysis of a global motion discrimination task with adaptive performance staircasing revealed that noradrenergic blockade (40 mg propranolol) significantly increased metacognitive performance (type-II area under the curve, AUROC2), but had no impact on perceptual decision making performance. Blockade of dopamine D2/3 receptors (400 mg amisulpride) had no effect on either metacognition or perceptual decision making. Our study is the first to show a pharmacological enhancement of metacognitive performance, in the absence of any effect on perceptual decision making. This enhancement points to a regulatory role for noradrenergic neurotransmission in perceptual metacognition.
The effect of piribedil on L-DOPA-induced dyskinesias in a rat model of Parkinson’s disease: differential role of α(2) adrenergic mechanisms
- Journal of neural transmission (Vienna, Austria : 1996)
- Published over 8 years ago
Piribedil is a non-ergoline, dopamine D(2)/D(3) receptor agonist with α(2) adrenoceptor antagonist properties that has been used in the treatment of Parkinson’s disease (PD). Noradrenergic neurotransmission may be involved in the pathogenesis of dyskinesias induced by chronic treatment with L-DOPA (3,4-dihydroxyphenylalanine, levodopa), but its role in the in vivo action of piribedil or on different subclasses of abnormal involuntary movements (AIMs) remains unclear. The aims of this study were therefore (1) to investigate the anti-dyskinetic effects of piribedil on L-DOPA-induced contralateral turning behaviour, locomotive dyskinesias (LD), axial dystonia (AD), orolingual dyskinesia (OD) and forelimb dyskinesia (FD) and (2) to compare these effects to the α(2) adrenoceptor antagonist, idazoxan, or the α(2) adrenoceptor agonist, clonidine. Rats were unilaterally lesioned with 6-hydroxydopamine (6-OHDA) and injected intraperitoneally twice daily with L-DOPA methylester (12.5 mg/kg) and benserazide (3.25 mg/kg). After 3 weeks, the effects of piribedil (5, 15, 40 mg/kg), clonidine (0.15 mg/kg), idazoxan (10 mg/kg) and combinations of these drugs were scored during 2 h. Pre-treatment with 5 and 40 mg/kg, but not 15 mg/kg, of piribedil reduced turning behaviour and AD, OD and FD, but piribedil increased LD at the 40 mg/kg doses compared to the L-DOPA group. Idazoxan induced similar effects as piribedil (40 mg/kg), except that it had no effect on LD. Idazoxan blocked the effect of piribedil on AD and FD. Clonidine reduced all AIMs except OD, possibly because of its sedative effect. Clonidine blocked the effect of piribedil on AD, OD and FD. These data suggest a differential involvement of α(2) adrenergic receptors in the action of piribedil on different subclasses of L-DOPA-induced dyskinesias.
Little is known about the evolutionary relationship between vertebrate adrenergic receptors and invertebrate octopamine and tyramine receptors. The complexity of the adrenergic signalling system is believed to be an innovation of the vertebrate lineage but the presence of noradrenaline has been reported in some invertebrate species. The cephalochordate, amphioxus (Branchiostoma floridae), is an ideal model organism for studying the evolution of vertebrate GPCRs, given its unique position at the base of the chordate lineage. Here, we describe the pharmacological characterisation and second messenger coupling abilities of AmphiAmR4, which clusters with α(2)-adrenergic receptors in a phylogenetic tree but also shares a high sequence similarity to invertebrate octopamine/tyramine receptors in both BLAST and Hidden Markov Model analyses. Thus, it was of particular interest to determine if AmphiAmR4 displayed similar functional properties to the vertebrate α(2)-adrenergic receptors or to invertebrate octopamine or tyramine receptors. When stably expressed in Chinese hamster ovary (CHO) cells, noradrenaline couples the receptor to both the activation of adenylyl cyclase and to the activation of the MAPKinase pathway. Pharmacological studies with a wide range of agonists and antagonists suggest that AmphiAmR4 functions as an α(2)-adrenergic-like receptor when expressed in CHO cells.
OBJECTIVE:To review the place in therapy of mirabegron, a new oral β3-adrenergic receptor agonist, for the treatment of overactive bladder (OAB).DATA SOURCES:A literature search of MEDLINE and MEDLINE In-Process & Other Non-Indexed Citations Databases (1996-April 2013) was conducted using the key words mirabegron, receptor, adrenergic, beta-3; adrenergic beta-3 receptor; beta-3 receptor, and overactive bladder; urinary bladder; overactive. All published articles regarding mirabegron were included. References of selected articles, data from poster presentations, and abstract publications were additionally reviewed.STUDY SELECTION AND DATA EXTRACTION:Available English-language data from reviews, abstracts, presentations, and clinical trials of mirabegron in humans were reviewed; relevant clinical data were selected and included.DATA SYNTHESIS:Mirabegron is the newest option for treatment of OAB with symptoms of urge incontinence. As a β3-receptor agonist, it reduces bladder muscle contractions. In two 12-week, randomized, double-blind, placebo-controlled Phase 3 studies, mirabegron significantly reduced the number of incontinence episodes per 24 hours from baseline (-1.47, -1.63, and -1.13; p < 0.05; and -1.57, -1.46, and -1.17; p < 0.05; all values for mirabegron 50 mg, 100 mg, and placebo). Micturitions per 24 hours were also reduced from baseline (-1.66, -1.75, and -1.05; p < 0.05; and -1.93, -1.77, and -1.34; p < 0.05; all values for mirabegron 50 mg, 100 mg, and placebo). A 12-month trial found mirabegron to have a safety and efficacy profile similar to that of tolterodine.CONCLUSIONS:Treatment of OAB initially includes lifestyle and nonpharmacologic intervention; for patients with persistent symptoms despite these treatments, drug therapy represents a next-step approach for symptom control. Mirabegron alleviates symptoms of OAB while having a mechanism of action that provides an alternative for patients who are intolerant of or who have contraindications to anticholinergic agents. The place in therapy of mirabegron relative to anticholinergics in the treatment of urge incontinence has not yet been established.
Therapeutic targeting of the beta-adrenergic receptors has recently shown remarkable efficacy in the treatment of benign vascular tumors such as infantile hemangiomas. As infantile hemangiomas are reported to express high levels of beta adrenergic receptors, we examined the expression of these receptors on more aggressive vascular tumors such as hemangioendotheliomas and angiosarcomas, revealing beta 1, 2, and 3 receptors were indeed present and therefore aggressive vascular tumors may similarly show increased susceptibility to the inhibitory effects of beta blockade. Using a panel of hemangioendothelioma and angiosarcoma cell lines, we demonstrate that beta adrenergic inhibition blocks cell proliferation and induces apoptosis in a dose dependent manner. Beta blockade is selective for vascular tumor cells over normal endothelial cells and synergistically effective when combined with standard chemotherapeutic or cytotoxic agents. We demonstrate that inhibition of beta adrenergic signaling induces large scale changes in the global gene expression patterns of vascular tumors, including alterations in the expression of established cell cycle and apoptotic regulators. Using in vivo tumor models we demonstrate that beta blockade shows remarkable efficacy as a single agent in reducing the growth of angiosarcoma tumors. In summary, these experiments demonstrate the selective cytotoxicity and tumor suppressive ability of beta adrenergic inhibition on malignant vascular tumors and have laid the groundwork for a promising treatment of angiosarcomas in humans.
Adrenergic urticaria (AU) is a rare type of stress-induced physical urticaria characterized by widespread pruritic urticarial papules. Diagnosis can be made by i.d. injection of adrenaline or noradrenaline, which produces the characteristic rash. Although the lesions of AU typically respond to beta-blockers such as propranolol, the therapeutic options for AU are limited. Here, we report a case of AU that was resistant to beta-blockers and successfully treated with clotiazepam. The clinical picture of AU resembles that of cholinergic urticaria (CU), however, positive noradrenaline test and negative acetylcholine skin test were useful for the differential diagnosis of AU and CU. Although his symptoms were resistant to several therapeutic methods including olopatadine (H1 antagonist), lafutidine (H2 antagonist) and propranolol, the severity and frequency of his attacks and his subjective symptoms were reduced by oral clotiazepam, an anxiolytic benzodiazepine. Dermatologists should be aware that anxiolytic benzodiazepines may be a therapeutic option in AU.
Connecting with others increases happiness, but strangers in close proximity routinely ignore each other. Why? Two reasons seem likely: Either solitude is a more positive experience than interacting with strangers, or people misunderstand the consequences of distant social connections. To examine the experience of connecting to strangers, we instructed commuters on trains and buses to connect with a stranger near them, to remain disconnected, or to commute as normal (Experiments 1a and 2a). In both contexts, participants reported a more positive (and no less productive) experience when they connected than when they did not. Separate participants in each context, however, expected precisely the opposite outcome, predicting a more positive experience in solitude (Experiments 1b and 2b). This mistaken preference for solitude stems partly from underestimating others' interest in connecting (Experiments 3a and 3b), which in turn keeps people from learning the actual consequences of social interaction (Experiments 4a and 4b). The pleasure of connection seems contagious: In a laboratory waiting room, participants who were talked to had equally positive experiences as those instructed to talk (Experiment 5). Human beings are social animals. Those who misunderstand the consequences of social interactions may not, in at least some contexts, be social enough for their own well-being. (PsycINFO Database Record © 2014 APA, all rights reserved).
- The Journal of pharmacology and experimental therapeutics
- Published over 7 years ago
Cocaine is a commonly abused illicit drug that causes significant morbidity and mortality. Although there is no true antidote to cocaine toxicity, current management strategies address the life-threatening systemic effects, namely hyperthermia, vasospasm, and severe hypertension. Clinicians rely on rapid cooling, benzodiazepines, and alpha adrenergic antagonists for management, with years of proven benefit. Experimental agents have been developed to more effectively treat acute toxicity. Pharmacodynamic approaches include antipsychotics that are thought to interfere with cocaine’s actions at several neurotransmitter receptors. These medications may worsen the consequences of cocaine toxicity though as they can interfere with heat dissipation, cause arrhythmias and lower the seizure threshold. Pharmacokinetic approaches employ cocaine metabolizing enzymes, such as butyrylcholinesterase (BChE), cocaine hydrolase (CocH), and bacterial cocaine esterase (CocE). Experimental models with these therapies improve survival, primarily when administered prior to cocaine, though newer evidence demonstrates beneficial effects shortly after cocaine toxicity has manifested. CocE, being a foreign protein, can induce an immune response with antibody formation. When enzyme administration is combined with vaccination against the cocaine molecule, improvement in cocaine-induced locomotor activity is observed. Finally, lipid emulsion rescue has been described in human case reports as an effective treatment in patients with hemodynamic compromise due to cocaine, which correlates well with its documented benefit in toxicity due to other local anesthetics. A pharmaceutical developed from these concepts will need to be expedient in onset and effective with minimal adverse effects, while at the same time being economical.
Enhancing the maturation of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) will facilitate their applications in disease modeling and drug discovery. Previous studies suggest that cell alignment could enhance hPSC-CM maturation; however, the robustness of this approach has not been well investigated. To this end, we examined if the anisotropic orientation of hPSC-CMs imposed by the underlying aligned fibers within a 3D microenvironment could improve the maturation of hPSC-CMs. Enriched hPSC-CMs were cultured for two weeks on Matrigel-coated anisotropic (aligned) and isotropic (random) polycaprolactone (PCL) fibrous scaffolds, as well as tissue culture polystyrenes (TCPs) as a control. As expected, hPSC-CMs grown on the two types of fibrous scaffolds exhibited anisotropic and isotropic orientations, respectively. Similar to cells on TCPs, hPSC-CMs cultured on these scaffolds expressed CM-associated proteins and were pharmacologically responsive to adrenergic receptor agonists, a muscarinic agonist, and a gap junction uncoupler in a dose-dependent manner. Although hPSC-CMs grown on anisotropic fibrous scaffolds displayed the highest expression of genes encoding a number of sarcomere proteins, calcium handling proteins and ion channels, their calcium transient kinetics were slower than cells grown on TCPs. These results suggest that electrospun anisotropic fibrous scaffolds, as a single method, have limited effect on improving the maturation of hPSC-CMs.