| 41. |
- Birnir, Bryndis, et al.
(författare)
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Bicuculline, pentobarbital and diazepam modulate spontaneous GABA(A) channels in rat hippocampal neurons
- 2000
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Ingår i: British Journal of Pharmacology. - : Wiley. - 1476-5381 .- 0007-1188. ; 131:4, s. 695-704
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Tidskriftsartikel (refereegranskat)abstract
- Spontaneously opening, chloride-selective channels that showed outward rectification were recorded in ripped-off patches from rat cultured hippocampal neurons and in cell-attached patches from rat hippocampal CA1 pyramidal neurons in slices. In both preparations, channels had multiple conductance states and the most common single-channel conductance varied. In the outside-out patches it ranged from 12 to 70 pS (Vp=40 mV) whereas in the cell-attached patches it ranged from 56 to 85 pS (-Vp=80 mV). Application of GABA to a patch showing spontaneous channel activity evoked a rapid, synchronous activation of channels. During prolonged exposure to either 5 or 100 microM GABA, the open probability of channels decreased. Application of GABA appeared to have no immediate effect on single-channel conductance. Exposure of the patches to 100 microM bicuculline caused a gradual decrease on the single-channel conductance of the spontaneous channels. The time for complete inhibition to take place was slower in the outside-out than in the cell-attached patches. Application of 100 microM pentobarbital or 1 microM diazepam caused 2 - 4 fold increase in the maximum channel conductance of low conductance (<40 pS) spontaneously active channels. The observation of spontaneously opening GABA(A) channels in cell-attached patches on neurons in slices suggests that they may have a role in neurons in vivo and could be an important site of action for some drugs such as benzodiazepines, barbiturates and general anaesthetics.
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| 42. |
- Eghbali, M, et al.
(författare)
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Pentobarbital modulates gamma-aminobutyric acid-activated single-channel conductance in rat cultured hippocampal neurons.
- 2000
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Ingår i: Molecular Pharmacology. - 0026-895X .- 1521-0111. ; 58:3, s. 463-9
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Tidskriftsartikel (refereegranskat)abstract
- We examined the effect of a range of pentobarbital concentrations on 0.5 microM gamma-aminobutyric acid (GABA)-activated channels (10 +/- 1 pS) in inside-out or outside-out patches from rat cultured hippocampal neurons. The conductance increased from 12 +/- 4 to 62 +/- 9 pS as the pentobarbital concentration was raised from 10 to 500 microM and the data could be fitted by a Hill-type equation. At 100 microM pentobarbital plus 0.5 microM GABA, the conductance seemed to reach a plateau. The pentobarbital EC(50)(0.5 microM GABA) value was 22 +/- 4 microM and n was 1.9 +/- 0.5. In 1 mM pentobarbital plus 0.5 microM GABA, the single-channel conductance decreased to 34 +/- 8 pS. This apparent inhibition of channel conductance was relieved by 1 microM diazepam. The channel conductance was 64 +/- 6 pS in the presence of all three drugs. The channels were open more in the presence of both GABA and pentobarbital than in the presence of either drug alone. Pentobarbital alone (100 microM) activated channels with conductance (30 +/- 2 pS) and kinetic properties distinct from those activated by either GABA alone or GABA plus pentobarbital. Whether pentobarbital induces new conformations or promotes conformations observed in the presence of GABA alone cannot be determined from our study, but the results clearly show that it is the combination of drugs present that determines the single-channel conductance and the kinetic properties of the receptors.
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| 43. |
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| 44. |
- Skovgård, Katrine
(författare)
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Models and biomarkers of motor and neuropsychiatric complications in Parkinson’s disease
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Parkinson's disease (PD) is a neurodegenerative disorder characterised by typicalmotor symptoms that are caused by severe dopamine depletion in the cortico-basalganglia network. Parkinsonian motor symptoms are improved by dopaminergicmedications, the most effective being the dopamine precursor L-DOPA. Thiscompound exerts its motor effects by stimulating dopamine D1 and D2 receptors,whose expression are segregated between the movement-promoting and movement-suppressing pathways of the basal ganglia circuitry. As the disease progresses,treatment with L-DOPA give rise to involuntary movements (dyskinesia), whichlimits its utility. Drugs that directly stimulate dopamine receptors, referred to asdopamine agonists, are commonly used to delay the use of L-DOPA or reduce itsdosage. Although less prone to induce dyskinesia, dopamine agonists have a highliability to induce neuropsychiatric side effects, in particular, impulsive-compulsivebehaviours. However, it remains to be established whether pharmacotherapiescombining L-DOPA and dopamine agonists give rise to specific profiles of motorand non-motor complications.The overarching aim of this thesis is to develop improved experimental modelsto advance translational research on the motor and neuropsychiatric complicationsof PD therapy. Both well-established and new experimental models are used todefine correlations and causal links between regimens of dopaminergic treatment,behavioural changes, and biomarkers of network and cellular dysfunction in thecortico-basal ganglia system.Using in vivo local field potential recordings to study biomarkers of networkdysfunctions, we show that changes in broad-band oscillatory activities of cortico-striatal circuits are correlated to ongoing motions and do not reflect parkinsonian-specific states. Moreover, we demonstrate that dyskinesias induced by D1 receptorstimulation are associated with prominent narrowband cortico-striatal oscillationsin the high gamma range (70-110 Hz). Following treatment with a D2 agonist, thesenarrowband gamma oscillations are less pronounced, whereas this treatment inducesprominent theta oscillations (5-10 Hz) in the deep basal ganglia nuclei. Thus, thecomposition of the dopaminergic therapies might affect these neurophysiologicalbiomarkers and should be considered in future investigations.Next, using a set of pharmacological tools and markers of cellular dysfunctions,we show that adjuvant treatment with D2/3 agonists alters the pattern of dopamine-related neuroplasticity in the basal ganglia compared to L-DOPA monotherapy,despite similar dyskinetic behaviours. The antidyskinetic effects of compounds modulating D1 receptor signalling were stronger in L-DOPA-treated animals, whileNMDA receptor antagonists produced markedly larger effects in the combinedtreatment group. Thus, adjuvant dopamine agonist treatment has a significantimpact on the neuroplasticity and pharmacological response profiles of L-DOPA-induced dyskinesia. In a last study, we show that treatment with a D2/3 agonistinduces compulsive behaviours and impulsive decision-making in both intact andpartially dopamine-depleted rats regardless of L-DOPA coadministration.Taken together, the findings of this thesis shed new light on the maladaptivecellular changes and network dynamics through which dopaminergic pharmacotherapies for PD affects motor behaviours. Moreover, this thesis work reveals the importance of including realistic models of combined therapies in future translational research on L-DOPA-induced dyskinesia.
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| 45. |
- Blomgren, Klas, 1963, et al.
(författare)
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Pathological apoptosis in the developing brain
- 2007
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Ingår i: Apoptosis. - : Springer Science and Business Media LLC. - 1360-8185 .- 1573-675X. ; 12:5, s. 993-1010
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Forskningsöversikt (refereegranskat)abstract
- More than half of the initially-formed neurons are deleted in certain brain regions during normal development. This process, whereby cells are discretely removed without interfering with the further development of remaining cells, is called programmed cell death (PCD). The term apoptosis is used to describe certain morphological manifestations of PCD. Many of the effectors of this developmental cell death program are highly expressed in the developing brain, making it more susceptible to accidental activation of the death machinery, e.g. following hypoxia-ischemia or irradiation. Recent evidence suggests, however, that activation and regulation of cell death mechanisms under pathological conditions do not exactly mirror physiological, developmentally regulated PCD. It may be argued that the conditions after e.g. ischemia are not even compatible with the execution of PCD as we know it. Under pathological conditions cells are exposed to various stressors, including energy failure, oxidative stress and unbalanced ion fluxes. This results in parallel triggering and potential overshooting of several different cell death pathways, which then interact with one another and result in complex patterns of biochemical manifestations and cellular morphological features. These types of cell death are here called "pathological apoptosis," where classical hallmarks of PCD, like pyknosis, nuclear condensation and caspase-3 activation, are combined with non-PCD features of cell death. Here we review our current knowledge of the mechanisms involved, with special focus on the potential for therapeutic intervention tailored to the needs of the developing brain.
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| 46. |
- Chebli, Jasmine
(författare)
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Physiological roles of amyloid precursor protein in vivo - zebrafish as a model
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Amyloid-beta precursor protein (APP) is an evolutionarily conserved transmembrane protein expressed in many different tissues. APP belongs to a gene family consisting of two other APP-like proteins (APLP1 and APLP2). APP has been shown to be involved in biological processes such as neurite outgrowth, neuronal migration, synapse formation and plasticity, and cell-cell interactions. APP also plays a central role in the development of Alzheimer's disease (AD). APP's physiological role has been difficult to understand and despite all research is not yet completely understood. The purpose of this thesis was to study the role of APP during early development with zebrafish as the main model system. We have focused on the zebrafish's Apps and have tried to understand their function with the help of genetic knockout models created using the CRISPR / Cas9 method. We report that appb mutants have weakened cell adhesions that give rise to changes in cell organization. We also report that the appb mutants are smaller but develop into fertile and healthy adult individuals. We also found defects in the formation of the trigeminal ganglia (TG) and that Appb seems to have a role in cell-cell interaction. The more widespread TG also consisted of fewer nerve cells, indicating that Appb promotes nerve cell formation. Furthermore, our studies demonstrate APP expression in cilia on sensory nerve cells and ependymal cells covering the brain chambers. The conserved expression of APP in ependymal cilia in mice and humans suggest an important and preserved function. Zebrafish with mutated App were found to have defects in the formation of both cilia and cerebral ventricles. To identify new signalling pathways through which Appb controls these functions, we studied protein changes in appb mutants using mass spectrometry. These studies highlight changes that both confirm known and suggest new regulations by appb, especially in neural development, cell adhesion and in gene regulation. Finally, we tried to answer the underlying mechanisms behind compensation within the App family. We found that mutations in the app genes activate expression of homologous genes via so-called transcriptional adaptation. In conclusion, the findings reported in this thesis showed that App is implicated already in early cellular adhesion and sensory neuronal differentiation processes and is located to several sensory cilia in vivo. The use of zebrafish as a model organism allowed us to gain valuable knowledge on the physiological roles of App.
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| 47. |
- Gezelius, Henrik, 1977-, et al.
(författare)
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Conditional genetic labeling of the Renshaw cell population for functional studies of motor control
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The Renshaw cells were among the first interneurons to be characterized in the mammalian spinal cord. Although the basic function of recurrent inhibition to motor neurons, as well as the Renshaw cell connectivity to other neurons have been thoroughly studied, the exact functional role of the Renshaw cells in motor control is still unknown. To further characterize the role of Renshaw cells in spinal cord circuitry, we searched for candidate genes useful in the Cre-loxP system. It has been reported that the mRNA expression of nicotinic cholinergic receptor alpha 2 (Chrna2) is found in a restricted number of cells at the ventral rim in adult rat and mouse spinal cord. In our own search for genes with distinct ventral expression, we noted a similar restricted Chrna2 mRNA expression pattern in the mouse spinal cord at postnatal day (P) 11 and during development at embryonic day 14.5. Based on the fact that the gene product is a cholinergic receptor and the pattern of expression, the neurons are predicted to be Renshaw cells. The possibility that these cells were motor neurons was excluded, since Chrna2 and Vesicular acetylcholine were not co-expressed at P11. To further study this cell population, we have generated a transgenic mouse expressing Cre recombinase (Cre) under the control of the Chrna2 promoter region. To visualize the Cre-expressing cells, the Chrna2-Cre transgenic mouse were bred with a reporter mouse expressing β-galactosidase (β-gal) in the nucleus after loxP excision. As expected, spinal cord β-gal immunoreactivity was observed in a limited number of ventrally located cells in the Cre-bearing offspring. Co-labeling of β-gal with calbindin-28K, a known marker for Renshaw cells, indicated that a majority of the calbindin positive cells were also β-gal positive at the ventral rim where calbindin is specific. In addition, β-gal positive cells without observable calbindin were also detected. It is conceivable that Chrna2 is expressed in additional cells apart from Renshaw cells or that a previously unidentified Renshaw cell subpopulation does not express calbindin. Nonetheless, a mouse with Cre-activity restricted to Chrna2-expressing cells opens the possibility to functionally study a limited population of spinal cord interneurons through genetic techniques, with the ambition to explore the specific role of Renshaw cells in spinal cord circuitry and motor control.
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| 48. |
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| 49. |
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| 50. |
- Nguyen, Tho D. K., et al.
(författare)
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Visualization of Partial Exocytotic Content Release and Chemical Transport into Nanovesicles in Cells
- 2022
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Ingår i: Acs Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 16:3
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Tidskriftsartikel (refereegranskat)abstract
- For decades, "all-or-none"and "kiss-and-run"were thought to be the only major exocytotic release modes in cell-to-cell communication, while the significance of partial release has not yet been widely recognized and accepted owing to the lack of direct evidence for exocytotic partial release. Correlative imaging with transmission electron microscopy and NanoSIMS imaging and a dual stable isotope labeling approach was used to study the cargo status of vesicles before and after exocytosis; demonstrating a measurable loss of transmitter in individual vesicles following stimulation due to partial release. Model secretory cells were incubated with 13C-labeled l-3,4-dihydroxyphenylalanine, resulting in the loading of 13C-labeled dopamine into their vesicles. A second label, di-N-desethylamiodarone, having the stable isotope 127I, was introduced during stimulation. A significant drop in the level of 13C-labeled dopamine and a reduction in vesicle size, with an increasing level of 127I-, was observed in vesicles of stimulated cells. Colocalization of 13C and 127I- in several vesicles was observed after stimulation. Thus, chemical visualization shows transient opening of vesicles to the exterior of the cell without full release the dopamine cargo. We present a direct calculation for the fraction of neurotransmitter release from combined imaging data. The average vesicular release is 60% of the total catecholamine. An important observation is that extracellular molecules can be introduced to cells during the partial exocytotic release process. This nonendocytic transport process appears to be a general route of entry that might be exploited pharmacologically. © 2022 The Authors. Published by American Chemical Society.
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