Steroid hormone action involves binding to cognate intracellular receptors that, in turn, bind to... more Steroid hormone action involves binding to cognate intracellular receptors that, in turn, bind to respective response elements and thus modulate gene expression. The present study shows that the gonadal steroids, 17beta-estradiol and progesterone, may also act as functional antagonists at the 5-hydroxytryptamine type 3 (5-HT3) receptor in whole-cell voltage-clamp recordings of HEK 293 cells stably expressing the 5-HT3 receptor. Functional antagonistic properties at this ligand-gated ion channel could also be shown for 17alpha-estradiol, 17alpha-ethinyl-17beta-estradiol, mestranol, R 5020, testosterone, and allopregnanolone but not for pregnenolone sulfate and cholesterol. An antagonism at the 5-HT3 receptor could further be observed with the aromatic alcohol 4-dodecylphenol but not with phenol or ethanol. Thus, the modulation of 5-HT3 receptor function by steroids or alcohols is dependent on their respective molecule structure. The antagonistic action of steroids at the 5-HT3 receptor is not mediated via the serotonin binding site because the steroids did not alter the binding affinity of [3H]GR65630 to the 5-HT3 receptor, and kinetic experiments revealed a quite different response pattern to 17beta-estradiol when compared with the competitive antagonist metoclopramide. BSA-conjugated gonadal steroids labeled with fluorescein isothiocyanate bound to membranes of HEK 293 cells expressing the 5-HT3 receptor in contrast to native HEK 293 cells. However, there was no dose-dependent displacement of the binding of gonadal steroids to membranes of cells expressing the 5-HT3 receptor in binding experiments or fluorescence studies. Thus, gonadal steroids probably interact allosterically with the 5-HT3 receptor at the receptor-membrane interface. The functional antagonism of gonadal steroids at the 5-HT3 receptor may play a role for the development and course of nausea during pregnancy and of psychiatric disorders.
Merz Pharmaceuticals GmbH and Forest Laboratories Inc are developing neramexane, an oral N-methyl... more Merz Pharmaceuticals GmbH and Forest Laboratories Inc are developing neramexane, an oral N-methyl-D-aspartate antagonist, as a potential neuroprotectant for various central nervous system disorders, including Alzheimer's disease, and for the potential treatment of drug and alcohol dependence, and pain.
... Brown, SM, Peet, E., Manuck, SB, Williamson, DE, Dahl, RE, Ferrell, RE & Hariri, ... more ... Brown, SM, Peet, E., Manuck, SB, Williamson, DE, Dahl, RE, Ferrell, RE & Hariri, AR (2005) A regulatory variant of the human tryptophan hydroxylase-2 gene biases amygdala reactivity. Mol Psychiatry 10, 884888. ... Domenici, MR, Azad, SC, Marsicano, G., Schierloh, A., Wotjak ...
Manipulating the function of neurons and circuits that translate electrical and chemical signals ... more Manipulating the function of neurons and circuits that translate electrical and chemical signals into behavior represents a major challenges in neuroscience. In addition to optogenetic methods using light-activatable channels, pharmacogenetic methods with ligand induced modulation of cell signaling and excitability have been developed. However, they are largely based on ectopic expression of exogenous or chimera proteins. Now, we describe the remote and reversible expression of a Kir2.1 type potassium channel using the chemogenetic technique of small molecule induced protein stabilization. Based on shield1-mediated shedding of a destabilizing domain fused to a protein of interest and inhibition of protein degradation, this principle has been adopted for biomedicine, but not in neuroscience so far. Here, we apply this chemogenetic approach in brain research for the first time in order to control a potassium channel in a remote and reversible manner. We could show that shield1-mediated ectopic Kir2.1 stabilization induces neuronal silencing in vitro and in vivo in the mouse brain. We also validated this novel pharmacogenetic method in different neurobehavioral paradigms.The DD-Kir2.1 may complement the existing portfolio of pharmaco- and optogenetic techniques for specific neuron manipulation, but it may also provide an example for future applications of this principle in neuroscience research.
N-methyl-D-aspartate (NMDA) receptor antagonists have a potentially wide range of therapeutic app... more N-methyl-D-aspartate (NMDA) receptor antagonists have a potentially wide range of therapeutic applications. Unfortunately, potent NMDA receptor channel blockers produce phencyclidine-like psychotropic symptoms in humans and rodents, and thereby produce numerous side effects. However, recent data indicate that moderate-affinity, voltage-dependent, open-channel blockers, such as memantine and neramexane (MRZ 2/579) are useful therapeutics as they prevent the pathological activation of NMDA receptors but allow their physiological activity and should prove to be useful therapeutics in a wide range of CNS disorders. Indeed, memantine was recently registered in both Europe and the USA for the treatment of moderate-to-severe Alzheimer's disease (AD). Neramexane is under development as a potential neuroprotectant against various CNS disorders. Although the predicted therapeutic doses of neramexane were very well tolerated in male volunteers, unfortunately, recent Phase II/III clinical trials for moderate-to-severe AD delivered contradictory results. Neramexane also failed in a recent randomized controlled Phase II trial against drug abuse and depression. Although Phase Ib clinical trials for the indications of chronic pain showed positive results, Phase II results indicate no superiority to existing treatments. However, positive study results have been presented recently in a Phase IIb study on the treatment of tinnitus. A Phase III study for this indication is presently ongoing. Another promising application for neramexane as a neuroprotectant might be chronic neurodegeneration, such as Parkinson's disease, Huntington's disease, vascular dementia, frontal lobe dementia, Down's syndrome and AD.
Despite the overt need for improved treatment modalities in depression, efforts to develop concep... more Despite the overt need for improved treatment modalities in depression, efforts to develop conceptually novel antidepressants have been relatively unsuccessful so far. Here we present a translational approach combining results from hypothesis-free animal experiments with data from a genetic association study in depression. Comparing genes regulated by chronic paroxetine treatment in the mouse hippocampus with genes showing nominally significant association with antidepressant treatment response in two pharmacogenetic studies, the activin pathway was the only one to show this dual pattern of association and therefore selected as a candidate. We examined the regulation of activin A and activin receptor type IA mRNA following antidepressant treatment. We investigated the effects of stereotaxic infusion of activin into the hippocampus and the amygdala in a behavioural model of depression. To analyse whether variants in genes in the activin signalling pathway predict antidepressant treat...
An in vitro excitatory post-synaptic potential stimulation technique was used to examine the effe... more An in vitro excitatory post-synaptic potential stimulation technique was used to examine the effects of asiatic acid (a. acid), an isolated compound of Centella asiatica on excitatory postsynaptic potential (EPSP) in the rat hippocampal slices. Hippocampal slices 350 μrn thick were perfused with oxygenated artificial cerebrospinal fluid, and electrodes were placed in the cornu ammonis (CA1) region to record EPSP responses to stimulation of Schaffer collateral/commissural fibers. Gamma-aminobutyric acid (GABA) receptors ...
Steroid hormone action involves binding to cognate intracellular receptors that, in turn, bind to... more Steroid hormone action involves binding to cognate intracellular receptors that, in turn, bind to respective response elements and thus modulate gene expression. The present study shows that the gonadal steroids, 17beta-estradiol and progesterone, may also act as functional antagonists at the 5-hydroxytryptamine type 3 (5-HT3) receptor in whole-cell voltage-clamp recordings of HEK 293 cells stably expressing the 5-HT3 receptor. Functional antagonistic properties at this ligand-gated ion channel could also be shown for 17alpha-estradiol, 17alpha-ethinyl-17beta-estradiol, mestranol, R 5020, testosterone, and allopregnanolone but not for pregnenolone sulfate and cholesterol. An antagonism at the 5-HT3 receptor could further be observed with the aromatic alcohol 4-dodecylphenol but not with phenol or ethanol. Thus, the modulation of 5-HT3 receptor function by steroids or alcohols is dependent on their respective molecule structure. The antagonistic action of steroids at the 5-HT3 receptor is not mediated via the serotonin binding site because the steroids did not alter the binding affinity of [3H]GR65630 to the 5-HT3 receptor, and kinetic experiments revealed a quite different response pattern to 17beta-estradiol when compared with the competitive antagonist metoclopramide. BSA-conjugated gonadal steroids labeled with fluorescein isothiocyanate bound to membranes of HEK 293 cells expressing the 5-HT3 receptor in contrast to native HEK 293 cells. However, there was no dose-dependent displacement of the binding of gonadal steroids to membranes of cells expressing the 5-HT3 receptor in binding experiments or fluorescence studies. Thus, gonadal steroids probably interact allosterically with the 5-HT3 receptor at the receptor-membrane interface. The functional antagonism of gonadal steroids at the 5-HT3 receptor may play a role for the development and course of nausea during pregnancy and of psychiatric disorders.
Merz Pharmaceuticals GmbH and Forest Laboratories Inc are developing neramexane, an oral N-methyl... more Merz Pharmaceuticals GmbH and Forest Laboratories Inc are developing neramexane, an oral N-methyl-D-aspartate antagonist, as a potential neuroprotectant for various central nervous system disorders, including Alzheimer's disease, and for the potential treatment of drug and alcohol dependence, and pain.
... Brown, SM, Peet, E., Manuck, SB, Williamson, DE, Dahl, RE, Ferrell, RE & Hariri, ... more ... Brown, SM, Peet, E., Manuck, SB, Williamson, DE, Dahl, RE, Ferrell, RE & Hariri, AR (2005) A regulatory variant of the human tryptophan hydroxylase-2 gene biases amygdala reactivity. Mol Psychiatry 10, 884888. ... Domenici, MR, Azad, SC, Marsicano, G., Schierloh, A., Wotjak ...
Manipulating the function of neurons and circuits that translate electrical and chemical signals ... more Manipulating the function of neurons and circuits that translate electrical and chemical signals into behavior represents a major challenges in neuroscience. In addition to optogenetic methods using light-activatable channels, pharmacogenetic methods with ligand induced modulation of cell signaling and excitability have been developed. However, they are largely based on ectopic expression of exogenous or chimera proteins. Now, we describe the remote and reversible expression of a Kir2.1 type potassium channel using the chemogenetic technique of small molecule induced protein stabilization. Based on shield1-mediated shedding of a destabilizing domain fused to a protein of interest and inhibition of protein degradation, this principle has been adopted for biomedicine, but not in neuroscience so far. Here, we apply this chemogenetic approach in brain research for the first time in order to control a potassium channel in a remote and reversible manner. We could show that shield1-mediated ectopic Kir2.1 stabilization induces neuronal silencing in vitro and in vivo in the mouse brain. We also validated this novel pharmacogenetic method in different neurobehavioral paradigms.The DD-Kir2.1 may complement the existing portfolio of pharmaco- and optogenetic techniques for specific neuron manipulation, but it may also provide an example for future applications of this principle in neuroscience research.
N-methyl-D-aspartate (NMDA) receptor antagonists have a potentially wide range of therapeutic app... more N-methyl-D-aspartate (NMDA) receptor antagonists have a potentially wide range of therapeutic applications. Unfortunately, potent NMDA receptor channel blockers produce phencyclidine-like psychotropic symptoms in humans and rodents, and thereby produce numerous side effects. However, recent data indicate that moderate-affinity, voltage-dependent, open-channel blockers, such as memantine and neramexane (MRZ 2/579) are useful therapeutics as they prevent the pathological activation of NMDA receptors but allow their physiological activity and should prove to be useful therapeutics in a wide range of CNS disorders. Indeed, memantine was recently registered in both Europe and the USA for the treatment of moderate-to-severe Alzheimer's disease (AD). Neramexane is under development as a potential neuroprotectant against various CNS disorders. Although the predicted therapeutic doses of neramexane were very well tolerated in male volunteers, unfortunately, recent Phase II/III clinical trials for moderate-to-severe AD delivered contradictory results. Neramexane also failed in a recent randomized controlled Phase II trial against drug abuse and depression. Although Phase Ib clinical trials for the indications of chronic pain showed positive results, Phase II results indicate no superiority to existing treatments. However, positive study results have been presented recently in a Phase IIb study on the treatment of tinnitus. A Phase III study for this indication is presently ongoing. Another promising application for neramexane as a neuroprotectant might be chronic neurodegeneration, such as Parkinson's disease, Huntington's disease, vascular dementia, frontal lobe dementia, Down's syndrome and AD.
Despite the overt need for improved treatment modalities in depression, efforts to develop concep... more Despite the overt need for improved treatment modalities in depression, efforts to develop conceptually novel antidepressants have been relatively unsuccessful so far. Here we present a translational approach combining results from hypothesis-free animal experiments with data from a genetic association study in depression. Comparing genes regulated by chronic paroxetine treatment in the mouse hippocampus with genes showing nominally significant association with antidepressant treatment response in two pharmacogenetic studies, the activin pathway was the only one to show this dual pattern of association and therefore selected as a candidate. We examined the regulation of activin A and activin receptor type IA mRNA following antidepressant treatment. We investigated the effects of stereotaxic infusion of activin into the hippocampus and the amygdala in a behavioural model of depression. To analyse whether variants in genes in the activin signalling pathway predict antidepressant treat...
An in vitro excitatory post-synaptic potential stimulation technique was used to examine the effe... more An in vitro excitatory post-synaptic potential stimulation technique was used to examine the effects of asiatic acid (a. acid), an isolated compound of Centella asiatica on excitatory postsynaptic potential (EPSP) in the rat hippocampal slices. Hippocampal slices 350 μrn thick were perfused with oxygenated artificial cerebrospinal fluid, and electrodes were placed in the cornu ammonis (CA1) region to record EPSP responses to stimulation of Schaffer collateral/commissural fibers. Gamma-aminobutyric acid (GABA) receptors ...
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