Browsing by Subject "neuroplasticity"
Now showing items 1-6 of 6
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(2022)In recent years, psychedelics have shown promise in the treatment of conditions like depression and addiction. The therapeutic effects of psychedelics have been linked to their ability to increase plasticity in the brain, an effect that has also been seen for antidepressants. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family, which has an important role in the development of the nervous system, as well as promotion of neuronal survival and differentiation during adulthood. BDNF, through its receptor TrkB, has been implicated in antidepressant action, and BDNF-TrkB signalling is involved in many aspects of plasticity. Recently, antidepressants have been reported to bind directly to TrkB, and through this binding mediate their plasticity-enhancing, as well as behavioural effects. Psychedelics have been shown to increase structural and functional plasticity, but the mechanisms behind these effects are not fully understood. For example, the serotonergic receptor 5-HT2A is known to be behind the acute hallucinogenic effects of psychedelics, but its role in plasticity is still debated. The aim of this study was to investigate the mechanisms of LSD-induced plasticity. The dimerization of TrkB was examined after LSD treatment in the protein-fragment complementation assay (PCA). Phosphorylation of TrkB signalling markers mTOR and ERK, which have known effects on plasticity, was assessed in Western blot, and the total expression of BDNF was examined with the enzyme-linked immunosorbent assay (ELISA). The timeline of the effects was investigated, and the involvement of 5-HT2A in TrkB dimerization and the phosphorylation of ERK was assessed by combining LSD treatment with the 5-HT2A antagonist M100907. Dimerization was also assessed in a TrkB mutant (Y433F) that has previously been shown to disrupt antidepressant effects on plasticity. These experiments showed that LSD treatment increased TrkB dimerization as well as phosphorylation of mTOR and ERK. The Y433F mutation interfered with LSD-induced TrkB dimerization, but the effects of LSD on TrkB dimerization or ERK phosphorylation were not blocked by M100907. Together, these data suggest that 5-HT2A is not involved in LSD-induced promotion of TrkB dimerization or ERK phosphorylation. The increases in phosphorylation and dimerization were found to be most robust after a 1 h LSD treatment, however an increase in BDNF expression was seen in cortical neuron cultures only after a 24 h treatment with LSD. The results reported in this study support the view that 5-HT2A might not be needed for the plasticity-inducing effects of psychedelics. If this is true, the development of treatments that target plasticity without hallucinatory effects could be possible. Overall, this research provides insight into the mechanisms of LSD-induced plasticity and offers new and interesting directions for future research in the field.
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(2022)In recent years, psychedelics have shown promise in the treatment of conditions like depression and addiction. The therapeutic effects of psychedelics have been linked to their ability to increase plasticity in the brain, an effect that has also been seen for antidepressants. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family, which has an important role in the development of the nervous system, as well as promotion of neuronal survival and differentiation during adulthood. BDNF, through its receptor TrkB, has been implicated in antidepressant action, and BDNF-TrkB signalling is involved in many aspects of plasticity. Recently, antidepressants have been reported to bind directly to TrkB, and through this binding mediate their plasticity-enhancing, as well as behavioural effects. Psychedelics have been shown to increase structural and functional plasticity, but the mechanisms behind these effects are not fully understood. For example, the serotonergic receptor 5-HT2A is known to be behind the acute hallucinogenic effects of psychedelics, but its role in plasticity is still debated. The aim of this study was to investigate the mechanisms of LSD-induced plasticity. The dimerization of TrkB was examined after LSD treatment in the protein-fragment complementation assay (PCA). Phosphorylation of TrkB signalling markers mTOR and ERK, which have known effects on plasticity, was assessed in Western blot, and the total expression of BDNF was examined with the enzyme-linked immunosorbent assay (ELISA). The timeline of the effects was investigated, and the involvement of 5-HT2A in TrkB dimerization and the phosphorylation of ERK was assessed by combining LSD treatment with the 5-HT2A antagonist M100907. Dimerization was also assessed in a TrkB mutant (Y433F) that has previously been shown to disrupt antidepressant effects on plasticity. These experiments showed that LSD treatment increased TrkB dimerization as well as phosphorylation of mTOR and ERK. The Y433F mutation interfered with LSD-induced TrkB dimerization, but the effects of LSD on TrkB dimerization or ERK phosphorylation were not blocked by M100907. Together, these data suggest that 5-HT2A is not involved in LSD-induced promotion of TrkB dimerization or ERK phosphorylation. The increases in phosphorylation and dimerization were found to be most robust after a 1 h LSD treatment, however an increase in BDNF expression was seen in cortical neuron cultures only after a 24 h treatment with LSD. The results reported in this study support the view that 5-HT2A might not be needed for the plasticity-inducing effects of psychedelics. If this is true, the development of treatments that target plasticity without hallucinatory effects could be possible. Overall, this research provides insight into the mechanisms of LSD-induced plasticity and offers new and interesting directions for future research in the field.
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(2016)Pharmacologically induced neuronal plasticity holds unprecedented potential in treatment of several neurological disorders, such as depression. Several antidepressant drugs have been shown to induce neuronal plasticity by stimulating BDNF (brain-derived neurotrophic factor) receptor TrkB (tropomyosin receptor kinase B). Studies with rapid-acting antidepressant treatments suggest delta range slow wave EEG (electroencephalography) activity to function as a potential non-invasive biomarker for activation of TrkB-related neuroplastic signaling responses. A sedative GABAA-agonist THIP (gaboxadol) has been shown to induce slow wave EEG activity (SWA) and preliminary studies suggest it to activate TrkB signaling as well. The aim of the present study was to examine the potential connection between SWA, neuroplastic signaling responses and neuronal inhibition by utilizing EEG measurements and THIP administration in genetic and developmental mouse models. The pharmaco-EEG experiments showed acute THIP administration (6 mg/kg, i.p.) to increase SWA in wild-type but not in GABAA δ-subunit knockout mice. TrkB signaling responses from similar treatment groups showed a trend of increased TrkB-related protein phosphorylation in wild-type but not in GABAA δ-subunit knockout mice indicating a positive connection between SWA, neuronal inhibition and TrkB-related signaling response. Autophosphorylation response of TrkB and related proteins in mice of different age showed most TrkB phosphorylation in postnatal day 16 (P16) mouse pups, whereas phosphorylation response of CREB and p70S6k was the highest in postnatal day 8 (P8) mouse pups. Since SWA emerges during the second postnatal week in mice, the obtained result further supports the connection between SWA and TrkB signaling. Acute THIP administration caused no significant phosphorylation changes in P8 or P16 mouse pups. The results support the hypothesis of a positive connection between SWA, neuronal inhibition and TrkB-related signaling response. Further studies with different excitatory and inhibitory interventions are required to better understand the role of neuronal excitation and inhibition in TrkB signaling responses and corresponding EEG signatures.
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(2018)Currently, there is an undeniable need for more effective treatments of depression. The efficacy of traditional antidepressant drugs becomes apparent after multiple weeks of treatment. New advancements in depression treatments have been made, as glutamatergic NMDA-receptor antagonist ketamine is seen to ameliorate symptoms rapidly, even only hours after drug administration. Understanding ketamine’s mechanism of action as an antidepressant could enable the development of more effective antidepressant drugs. The critical molecular level component in ketamine’s antidepressant effect is considered to be the activation of TrkB tyrosine receptor kinase B, which subsequently leads to the initiation of signaling pathways, which regulate synaptic plasticity. So far, it has not been examined; whether there is a difference in ketamine’s antidepressant effect based on the dosing-time of day. The aim of the present study was to find out if there is a variation between ketamine’s effect on synaptic plasticity and the circadian phase in which the drug is administered. Ketamine’s (200 or 50 mg/kg, i.p.) effects were studied in C57BL/6J–mice during light phase (mouse’s inactive phase) and dark phase (mouse’s active phase) of the day. The phase of the day didn’t affect the activity of TrkB signaling in its related parts (pTrkBTyr816, pGSK3βSer9, p-p70S6KTyr421/Ser424 and p-p44/42MAPKThr202/Tyr204) in prefrontal cortex samples which were analysed in Western blot assay. Ketamine increased dose-dependently the phosphorylation of GSK3βSer9 and p70S6KTyr421/Ser424 as well as decreased p-p44/42MAPKThr202/Tyr204 at 30 minutes after drug administration in both phases of the day. Ketamine (200 mg/kg, i.p.) also lowered the glucose concentration measured from the trunk blood. To examine the effect of hypoglycemia on the activity of TrkB signaling another experiment was conducted. The hypoglycemia induced by insulin detemir (6 IU/kg, i.p.) didn’t affect any measured protein phosphorylation at 60 minutes after drug administration. The results of this study support the notion of ketamine’s rapid and dosedependent induction of neuroplasticity. The possible role of hypoglycemia in ketamine's neuropharmacology should be investigated in future studies.
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(2023)Myelin is a lipid-rich substance wrapped around nerve axons that can be adaptively modified in response to neuronal activity and experience. Recent research has revealed myelination of parvalbumin (PV) inhibitory interneurons, critical for brain oscillations and balance. Defects in PV interneuron myelination have been linked to psychiatric disorders, like schizophrenia. Tropomyosin receptor kinase B (TrkB) signaling has been shown to be important for myelination. Moreover, fluoxetine, an antidepressant, binds to TrkB receptors in PV interneurons, enhancing plasticity. While previous studies support the importance of PV interneuron mediated TrkB signaling for anti-depressant induced neural plasticity, its effect on PV interneuron myelination remains unexplored. The objective of this thesis was to investigate whether TrkB signaling, and fluoxetine affect the overall and PV-interneuron specific myelination in the medial prefrontal cortex (mPFC) in mice. Using immunohistochemical analysis, we assessed myelin changes through node of Ranvier morphology and myelin immunostaining intensity in control and in mice with heterozygous conditional TrkB deletion in PV interneurons (hereafter referred to as TrkB KO), with or without fluoxetine. We found that fluoxetine increases node length in TrkB KO mice, while reduced TrkB signaling shortens paranodes in PV neurons compared to controls. Our findings also depict that fluoxetine and PV-mediated TrkB signaling do not alter the overall myelination of the mPFC. The findings of this work provide mechanistic insights into PV interneuron myelination in the mPFC, with potential implications for demyelinating and psychiatric conditions where PV myelination plays a role.
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(2023)Myelin is a lipid-rich substance wrapped around nerve axons that can be adaptively modified in response to neuronal activity and experience. Recent research has revealed myelination of parvalbumin (PV) inhibitory interneurons, critical for brain oscillations and balance. Defects in PV interneuron myelination have been linked to psychiatric disorders, like schizophrenia. Tropomyosin receptor kinase B (TrkB) signaling has been shown to be important for myelination. Moreover, fluoxetine, an antidepressant, binds to TrkB receptors in PV interneurons, enhancing plasticity. While previous studies support the importance of PV interneuron mediated TrkB signaling for anti-depressant induced neural plasticity, its effect on PV interneuron myelination remains unexplored. The objective of this thesis was to investigate whether TrkB signaling, and fluoxetine affect the overall and PV-interneuron specific myelination in the medial prefrontal cortex (mPFC) in mice. Using immunohistochemical analysis, we assessed myelin changes through node of Ranvier morphology and myelin immunostaining intensity in control and in mice with heterozygous conditional TrkB deletion in PV interneurons (hereafter referred to as TrkB KO), with or without fluoxetine. We found that fluoxetine increases node length in TrkB KO mice, while reduced TrkB signaling shortens paranodes in PV neurons compared to controls. Our findings also depict that fluoxetine and PV-mediated TrkB signaling do not alter the overall myelination of the mPFC. The findings of this work provide mechanistic insights into PV interneuron myelination in the mPFC, with potential implications for demyelinating and psychiatric conditions where PV myelination plays a role.
Now showing items 1-6 of 6