ORCID Profile
0000-0001-7811-5383
Current Organisation
Lund University
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Publisher: PeerJ
Date: 02-10-2018
DOI: 10.7287/PEERJ.PREPRINTS.27248V1
Abstract: Optogenetics is revolutionizing neuroscience but an often neglected effect of light stimulation of the brain is the generation of heat. In extreme cases, light-generated heat kills neurons but mild temperature changes alter neuronal function. In this work, we investigated heat transfer in brain tissue for common optogenetic protocols using the finite element method. We then modeled channelrhodopsin-2 in a single- and a spontaneous-firing neuron to explore the effect of heat in light stimulated neurons. We found that, at commonly used intensities, laser radiation considerably increases the temperature in the surrounding tissue. This effect alters action potential size and shape and cause increase in spontaneous firing frequency in a neuron model. However, the shortening of activation time constants generated by heat in the single firing neuron model produce AP failures in response to light stimulation. We also found changes in the power spectrum density and a reduction in the time required for synchronization in an interneuron network model of gamma oscillations. Our findings indicate that light stimulation with intensities used in optogenetic experiments may affect neuronal function not only by direct excitation of light sensitive ion channels and/or pumps but also by generating heat. This approach serves as a guide to design optogenetic experiments that minimize the role of tissue heating in the experimental outcome.
Publisher: Frontiers Media SA
Date: 04-02-2020
Publisher: Wiley
Date: 15-02-2019
DOI: 10.1002/HIPO.23080
Abstract: Prolonged increases in excitation can trigger cell-wide homeostatic responses in neurons, altering membrane channels, promoting morphological changes, and ultimately reducing synaptic weights. However, how synaptic downscaling interacts with classical forms of Hebbian plasticity is still unclear. In this study, we investigated whether chronic optogenetic stimulation of hippoc us CA1 pyramidal neurons in freely moving mice could (a) cause morphological changes reminiscent of homeostatic scaling, (b) modulate synaptic currents that might compensate for chronic excitation, and (c) lead to alterations in Hebbian plasticity. After 24 hr of stimulation with 15-ms blue light pulses every 90 s, dendritic spine density and area were reduced in the CA1 region of mice expressing channelrhodopsin-2 (ChR2) when compared to controls. This protocol also reduced the litude of mEPSCs for both the AMPA and NMDA components in ex vivo slices obtained from ChR2-expressing mice immediately after the end of stimulation. Finally, chronic stimulation impaired the induction of LTP and facilitated that of LTD in these slices. Our results indicate that neuronal responses to prolonged network excitation can modulate subsequent Hebbian plasticity in the hippoc us.
Publisher: Cold Spring Harbor Laboratory
Date: 20-07-2023
DOI: 10.1101/2023.07.19.549676
Abstract: In the mammalian brain, new neurons continue to be generated throughout life in a process known as adult neurogenesis. The role of adult-generated neurons has been broadly studied across laboratories, and mounting evidence suggests a strong link to the HPA axis and concomitant malfunction in patients diagnosed with mood disorders. Psychedelic compounds, such as phenethylamines, tryptamines, cannabinoids, and a variety of ever-growing chemical categories, emerge as therapeutic options for neuropsychiatric disorders, while numerous reports link their effects to increased adult neurogenesis. In this systematic review, we examine studies assessing neurogenesis after psychedelics interventions and aim to provide a comprehensive picture of how this vast category of compounds regulates the generation of new neurons. Following PRISMA guidelines, we conducted a literature search on PubMed and Science Direct databases considering all articles published until January 31, 2022. We selected studies containing both the words “neurogenesis” and “psychedelics”, using either in vivo or in vitro models, and employing classical or atypical psychedelics at all ontogenetic windows. Of a total of 205 articles, 68 met all the necessary conditions for further review. Our findings were ided into five main categories of psychedelics: CB1 agonists, NMDA antagonists, harmala alkaloids, tryptamines, and entactogens. We then described the outcomes of neurogenesis assessments and investigated related results on the effects of psychedelics on brain plasticity and behavior within our s le. In summary, this review presents an extensive study into how different psychedelics may affect the birth of new neurons and other brain-related processes. Such knowledge may be valuable for future research on novel therapeutic strategies for neuropsychiatric disorders.
Publisher: Cold Spring Harbor Laboratory
Date: 11-05-2018
DOI: 10.1101/320507
Abstract: Prolonged increases in excitation can trigger cell-wide homeostatic responses in neurons, altering membrane channels, promoting morphological changes and ultimately reducing synaptic weights. However, how synaptic downscaling interacts with classical forms of Hebbian plasticity is still unclear. In this study, we investigated whether chronic optogenetic stimulation of hippoc us CA1 pyramidal neurons in freely-moving mice could (a) cause morphological changes reminiscent of homeostatic scaling, (b) modulate synaptic currents that might compensate for chronic excitation, and (c) lead to alterations in Hebbian plasticity. After 24 h of stimulation with 15-ms blue light pulses every 90 s, dendritic spine density and area were reduced in the CA1 region of mice expressing channelrhodopsin-2 (ChR2) when compared to controls. This protocol also reduced the litude of mEPSCs for both the AMPA and NMDA components in ex vivo slices obtained from ChR2-expressing mice immediately after the end of stimulation. Lastly, chronic stimulation impaired the induction of LTP and facilitated that of LTD in these slices. Our results indicate that neuronal responses to prolonged network excitation can modulate subsequent Hebbian plasticity in the hippoc us.
No related grants have been discovered for Thiago Moulin.