Biology subjects

Koutlas, I.

Publications and source records attributed to Koutlas, I..

3 recordsLinked to original sources

bioRxiv2024

Distinct ventral tegmental area neuronal ensembles are indispensable for reward-driven approach and stress-driven avoidance behaviors

Assigning valence to stimuli for adaptive behavior is an essential function, involving the ventral tegmental area (VTA). VTA cell types are often defined through neurotransmitters (NT). However, valence function in VTA does not parse along NT-boundaries as, within each NT-class, certain neurons are excited by reward and others by stressors. Here we identify the co-activated mouse VTA neuronal ensembles for reward and stress, and determine their role in adaptive behaviors. We show that stimuli of opposite valence (opioid vs acute social stress) recruit two segregated intermingled small VTA neuronal ensembles. These two ensembles continue to be preferentially engaged by congruent valence stimuli. Stimulation of VTA stress- or reward ensembles is aversive/reinforcing, respectively. Strikingly, external valence stimuli fully require activity of these small discrete VTA ensembles for conferring approach/avoidance outcomes. Overall, our study identifies distinct small VTA ensembles for positive and negative valence coding and shows their indispensability for adaptive behavior.

neuroscience↗

bioRxiv2022

GelMap: Intrinsic calibration and deformation mapping for expansion microscopy

Expansion microscopy (ExM) is a powerful technique to overcome the diffraction limit of light microscopy by physically expanding biological specimen in three dimensions. Nonetheless, using ExM for quantitative or diagnostic applications requires robust quality control methods to precisely determine expansion factors and to map deformations due to anisotropic expansion. Here we present GelMap, a flexible workflow to introduce a fluorescent grid into pre-expanded hydrogels that scales with expansion and reports deformations. We demonstrate that GelMap can be used to precisely determine the local expansion factor and to correct for deformations without the use of cellular reference structures or pre-expansion ground truth images. Moreover, we show that GelMap aids sample navigation for correlative uses of expansion microscopy. Finally, we show that GelMap is compatible with expansion of tissue and can be readily implemented as a quality control step into existing ExM workflows.

cell biology↗

bioRxiv2020

Single exposure to social defeat or immobilization stress fails to induce lasting alterations in general anxiety and hippocampal neurogenesis in Wistar and wild-type Groningen rats

Suppression of hippocampal neurogenesis is a readout for stress-induced alterations in neuroplasticity. In this study, we hypothesized that a single episode of severe social or non-social stress would differentially suppress neurogenesis in the dentate gyrus (DG) 10 days later in two rat strains. We anticipated that the suppression following social stress would be less severe in wildtype Groningen (WTG) rats, a rat strain considered relatively resilient to social stressors. Male Wistar and WTG were subjected to either social defeat or to immobilization stress. Behavioral response to social defeat and acute corticosterone response to both stressors was measured as well as anxiety behavior 10 days later on the elevated plus maze. Subsequently, brains were collected following cardiac aldehyde perfusion. The behavioral freezing response to defeat was much stronger in Wistar rats as compared to WTG rats. Acute corticosteroid response was similar in both strains although Wistar rats more rapidly resumed baseline values. There was no significant effect of both stressors on hippocampal DG cell proliferation and differentiation as well as on anxiety behavior. However, a striking strain difference appeared in anxiety behavior and both markers of neurogenesis. The WTG strain exhibiting much lower anxiety as well as reduced rate of hippocampal neurogenesis under all treatments. The results in this study suggest that both short-lasting acute stressors failed to induce lasting anxiety or decreased neurogenesis in the DG. Future studies could explore if and how rate of hippocampal neurogenesis is related with behavioral coping with stress.

neuroscience↗