Amyotrophic lateral sclerosis (ALS) is a progressive neurological disorder of the central nervous system characterized by loss of motor neurons and voluntary muscle degeneration. Astrocytes play a major role in regulation of the disease onset and progression due to their intimate association with neurons. Regulation of ionic homeostasis is one of their key functions and its failure has been linked to several neurological diseases. The aim of this thesis was to explore differences in membrane properties of astrocytes in ALS. To fulfill this aim, a double transgenic mouse strain with ALS-like phenotype and a specific expression of enhanced green fluorescent protein in astrocytes was generated. To phenotype this strain, two sensorimotor tests, wire grid hang test and rotarod test, were conducted. Immunohistochemistry was used to characterize the strain on a cellular level and to explore changes of specific ion channels. Functional properties of astrocytes were explored using the patch clamp technique. The double transgenic strain has the characteristic ALS-like phenotype and is comparable to the original strain with differences in symptom onset and progression between models and sexes. On the cellular level, there are characteristic ALS features, specifically loss of motor neurons and astrogliosis....

Mikrobielle Rhodopsine sind lichtsensitive Proteine, die von Mikroorganismen exprimiert werden um Licht wahrzunehmen oder dessen Energie zu nutzen. Ionen-transportierende mikrobielle Rhodopsine begründeten das Feld der Optogenetik. Hier erlauben sie transmembrane Ionenflüsse lichtsensitiv zu machen und neuronale Aktivität mit Licht zu steuern. Eine zielführende Nutzung beruht auf ihrer molekularen Charakterisierung, um sie dem Experiment anzupassen und es sinnvoll zu entwerfen. Teil I der Arbeit beschäftigt sich mit dem rotverschobenen Kanalrhodopsin ReaChR. Obwohl es mit breitem, nicht gaussförmigen Aktionsspektrum mit maximalen Strömen um 600 nm publiziert wurde, zeigte das Blitzlichtspektrum hier maximale Aktivität bei 535 nm ohne Besonderheiten. Mit steigender Intensität und längeren Pulsen verbreiterte sich das Spektrum; sehr ähnlich zum publizierten Spektrum. Dieses einzigartige Verhalten wird durch sekundäre Photochemie erklärt, welche zu einem komplexen Photozyklus mit lichtinduzierten Übergangen führt. Mutationen an Schlüsselpositionen wurden genutzt, um ReaChR über die publizierten Daten hinaus zu charakterisieren und neue Eigenschaften zu generieren. In Teil II wurde die auswärtsgerichtete Natriumpumpe KR2 elektrophysiologisch charakterisiert, was zuvor von schlechter Membranständigkeit in Säugetierzellen verhindert wurde. Ein verbessertes KR2 mit höherer Membranständigkeit und 60-fach größeren Photoströmen erlaubte Selektivitätsmessungen, welche zeigten, dass der Strom von Natriumionen getragen wird, wohingegen nichts auf Protonentransport hindeutete. Bei ausreichender Substratkonzentration war der Strom anders als bei Chlorid- oder Protonenpumpen von der Membranspannung unabhängig. Die Expression in Mausneuronen ermöglichte die reversible Unterdrückung von Aktionspotentialen mit Licht, wobei der Ausstrom von Kationen einen komplementären Weg zur neuronale Aktivitätsunterdrückung bietet, wenn etablierte Werkzeuge schlecht oder nicht funktionieren. / Microbial rhodopsins are photosensitive proteins utilized by fungi, algae, and prokaryotes to sense light or harness its' energy. Ion transporting microbial rhodopsins initiated the field of optogenetics, where they are applied to render transmembrane ion fluxes light sensitive and control neuronal activity with light. Part I of the thesis focused on the electrophysiological characterization of the red-shifted channelrhodopsin ReaChR. Although published with a broad, non-Gaussian shaped action spectrum peaking around 600 nm, the flash action spectra of ReaChR recorded here had a maximum at 535 nm without peculiarities. Increasing intensities and prolonging illumination broadened the spectrum, which finally peaked around 600 nm. This unique behavior stems from pronounced secondary photochemistry leading to a complex photocycle with various light-induced transitions especially under constant illumination. Mutations at key positions like the central gate, DC-pair or counter ions were employed to characterize the properties of ReaChR beyond published data and engineer new features. In part II an electrophysiological characterization of the outward Na+ pump KR2 was pursued, which was hindered by poor membrane targeting in mammalian cells before. Engineering of eKR2 improved membrane targeting and lead to 60-fold larger photocurrents than in the wild type. Selectivity measurements revealed that the stationary photocurrent is primarily carried by sodium with no evidence for proton transport. At sufficient substrate concentration stationary photocurrents were independent of the membrane voltage distinguishing eKR2 from proton and chloride pumps. Finally, eKR2 reliably and reversibly inhibited action potential firing already at 0.5 mW/mm2 green illumination in cultured hippocampal mouse neurons. Inhibiting action potential firing through cation extrusion poses a complementary way of neuronal silencing in contexts where established tools are unfavorable or even impossible to use.

The transmission of sex pheromone-mediated signals is essential for goldfish reproduction. However, the neural pathways underlying this reproductive signalling pathway in the goldfish brain is not well described. Lesioning experiments have shown previously that two brain areas, the preoptic area (POA) and the ventral telencephali pars ventralis (Vv) in particular, are important for reproduction. We used patch clamp electrophysiology to study the electrical activities of POA and Vv neurons. Based on the intrinsic properties of these neurons, we suggest there are five different functional classes of POA neurons and a single class of Vv neurons. In addition, by electrically stimulating the olfactory bulb (OB), we were able to show that this primary sensory structure makes monosynaptic glutamatergic connections with both POA and Vv neurons. While electrophysiology measures signalling events occurring at short time scales on the order of milliseconds to minutes, we were also interested in studying sex pheromone signalling in the goldfish brain over a long time scale. Thus, we describe changes in gene expression in male goldfish exposed to waterborne sex pheromones (17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha) over 6 hours. We perform cDNA microarrays on Prostaglandin-F2alpha-treated fish to study the rapid modulation of transcription and define the signalling pathways affected. Our microarrays showed that 71 genes were differentially regulated (67 up and 4 down). Through gene ontology enrichment analysis, we found that these genes were involved in various biological processes such as RNA processing, neurotransmission, neuronal development, apoptosis, cellular metabolism and sexual reproduction. RT-PCRs were performed to validate our microarrays and to facilitate direct comparisons of the effects of the two sex pheromones, 17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha. By combining electrophysiology and gene expression analyses, we were able to study sex-pheromone signalling on two different time scales. One short, occurring on the order of milliseconds to minutes, that involves electrical activities in the brain through the glutamatergic amino-3-hydroxy-5-methylisoxazole-4-propionate and N-methyl-D-aspartate receptors; and the other long occurring several hours later that involves changes in the gene expression levels of calmodulin and ependymin among other genes underlying neuroplasticity. Reproductive neuroplasticity in the goldfish may therefore require the activation of glutamatergic receptors which then activate downstream signals like calmodulin and ependymin to transform the sex pheromones-mediate signal into gene expression.

The transmission of sex pheromone-mediated signals is essential for goldfish reproduction. However, the neural pathways underlying this reproductive signalling pathway in the goldfish brain is not well described. Lesioning experiments have shown previously that two brain areas, the preoptic area (POA) and the ventral telencephali pars ventralis (Vv) in particular, are important for reproduction. We used patch clamp electrophysiology to study the electrical activities of POA and Vv neurons. Based on the intrinsic properties of these neurons, we suggest there are five different functional classes of POA neurons and a single class of Vv neurons. In addition, by electrically stimulating the olfactory bulb (OB), we were able to show that this primary sensory structure makes monosynaptic glutamatergic connections with both POA and Vv neurons. While electrophysiology measures signalling events occurring at short time scales on the order of milliseconds to minutes, we were also interested in studying sex pheromone signalling in the goldfish brain over a long time scale. Thus, we describe changes in gene expression in male goldfish exposed to waterborne sex pheromones (17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha) over 6 hours. We perform cDNA microarrays on Prostaglandin-F2alpha-treated fish to study the rapid modulation of transcription and define the signalling pathways affected. Our microarrays showed that 71 genes were differentially regulated (67 up and 4 down). Through gene ontology enrichment analysis, we found that these genes were involved in various biological processes such as RNA processing, neurotransmission, neuronal development, apoptosis, cellular metabolism and sexual reproduction. RT-PCRs were performed to validate our microarrays and to facilitate direct comparisons of the effects of the two sex pheromones, 17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha. By combining electrophysiology and gene expression analyses, we were able to study sex-pheromone signalling on two different time scales. One short, occurring on the order of milliseconds to minutes, that involves electrical activities in the brain through the glutamatergic amino-3-hydroxy-5-methylisoxazole-4-propionate and N-methyl-D-aspartate receptors; and the other long occurring several hours later that involves changes in the gene expression levels of calmodulin and ependymin among other genes underlying neuroplasticity. Reproductive neuroplasticity in the goldfish may therefore require the activation of glutamatergic receptors which then activate downstream signals like calmodulin and ependymin to transform the sex pheromones-mediate signal into gene expression.

The transmission of sex pheromone-mediated signals is essential for goldfish reproduction. However, the neural pathways underlying this reproductive signalling pathway in the goldfish brain is not well described. Lesioning experiments have shown previously that two brain areas, the preoptic area (POA) and the ventral telencephali pars ventralis (Vv) in particular, are important for reproduction. We used patch clamp electrophysiology to study the electrical activities of POA and Vv neurons. Based on the intrinsic properties of these neurons, we suggest there are five different functional classes of POA neurons and a single class of Vv neurons. In addition, by electrically stimulating the olfactory bulb (OB), we were able to show that this primary sensory structure makes monosynaptic glutamatergic connections with both POA and Vv neurons. While electrophysiology measures signalling events occurring at short time scales on the order of milliseconds to minutes, we were also interested in studying sex pheromone signalling in the goldfish brain over a long time scale. Thus, we describe changes in gene expression in male goldfish exposed to waterborne sex pheromones (17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha) over 6 hours. We perform cDNA microarrays on Prostaglandin-F2alpha-treated fish to study the rapid modulation of transcription and define the signalling pathways affected. Our microarrays showed that 71 genes were differentially regulated (67 up and 4 down). Through gene ontology enrichment analysis, we found that these genes were involved in various biological processes such as RNA processing, neurotransmission, neuronal development, apoptosis, cellular metabolism and sexual reproduction. RT-PCRs were performed to validate our microarrays and to facilitate direct comparisons of the effects of the two sex pheromones, 17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha. By combining electrophysiology and gene expression analyses, we were able to study sex-pheromone signalling on two different time scales. One short, occurring on the order of milliseconds to minutes, that involves electrical activities in the brain through the glutamatergic amino-3-hydroxy-5-methylisoxazole-4-propionate and N-methyl-D-aspartate receptors; and the other long occurring several hours later that involves changes in the gene expression levels of calmodulin and ependymin among other genes underlying neuroplasticity. Reproductive neuroplasticity in the goldfish may therefore require the activation of glutamatergic receptors which then activate downstream signals like calmodulin and ependymin to transform the sex pheromones-mediate signal into gene expression.

Molecular mechanism of Cannabinoid receptor 1 regulation by SGIP1 Abstract Src homology 3-domain growth factor receptor-bound 2-like endophilin interacting protein 1 (SGIP1) has been identified as an interacting partner of cannabinoid receptor 1 (CB1R). Their protein-protein interaction was confirmed by co-immunoprecipitation. SGIP1 hinders the internalization of activated CB1R and modulates its signaling in HEK293 cells. Employing whole-cell patch-clamp electrophysiology, we have shown that SGIP1 affects CB1R signaling in autaptic hippocampal neurons. Using a battery of behavioral tests in SGIP1 constitutive knock-out (SGIP1-/- ) and WT mice, we investigated the consequences of SGIP1 deletion on behavior regulated by the endocannabinoid system. In SGIP1-/- mice, exploratory levels, working memory and sensorimotor gating were unaltered. SGIP1-/- mice showed decreased anxiety-like and depressive-like behaviors. Fear extinction to tone was enhanced in SGIP1-/- females. Several cannabinoid tetrad behaviors were altered in the absence of SGIP1. SGIP1-/- males exhibited abnormal THC withdrawal behaviors. SGIP1 deletion also reduced acute nociception, and SGIP1-/- mice were more sensitive to antinociceptive effects of CB1R agonists and morphine. CB1R-SGIP1 interaction results in profound modification of CB1R...

The risks of damage to the developing nervous system of many chemicals are not known because these studies often require costly and time-consuming multi-generational animal experiments. Pluripotent stem cell-based systems can facilitate developmental neurotoxicity studies because disturbances in nervous system development can be modeled in vitro. In this study, neurons derived from embryonal carcinoma (EC) and induced pluripotent stem (iPS) cells, were first characterized to establish their suitability for developmental neurotoxicity studies. The EC stem cell line, TERA2.cl.SP-12, was differentiated into neurons that expressed voltage-gated sodium and potassium channels as well as ionotropic GABA and glutamate receptors. These cells could also fire action potentials when stimulated electronically. However spontaneous action potentials were not observed. In contrast, pre-differentiated neurons derived from iPS cells fired evoked and spontaneous action potentials. Furthermore, iPS cell-derived neurons also expressed a wide array of functional voltage- and ligand-gated ion channels. Antiepileptic drugs (AEDs) are associated with developmental neurotoxicity. These agents can cause congenital malformations, cognitive deficits and behavioral impairment in children as a result of in utero exposure. The impact of four major AEDs, namely phenobarbital, valproic acid, carbamazepine and lamotrigine, on cell viability, cell cycle and differentiation of TERA2.cl.SP-12 into neurons was studied. All AEDs tested reduced differentiating stem cell viability. Valproic acid and carbamazepine increased apoptosis and reduced cell proliferation. A brief exposure to phenobarbital, valproic acid and lamotrigine at the start of differentiation impaired the subsequent generation of neurons. Additionally, the effect of transient exposure to phenobarbital and carbamazepine on neuronal maturation of iPS-derived neurons was investigated. Exposure to both AEDs resulted in diminished membrane potentials and reduced the proportion of cells that were able to fire action potentials spontaneously in culture. The data from these studies suggest that impairments in proliferation, differentiation and maturation of neurons derived from human stem cells may be sensitive indicators of neurodevelopmental disruption by these drugs that can result from in utero exposure. Furthermore, these findings suggest that the use of human pluripotent stem cells and neurons derived from them can reduce the time, cost and the number of animals used in toxicological research.