Biology subjects

Luna, V. M.

Publications and source records attributed to Luna, V. M..

3 recordsLinked to original sources

bioRxiv2024

Effects of electroconvulsive shock on the function, circuitry, and transcriptome of dentate gyrus granule neurons

Therapeutic use of electroconvulsive shock (ECS) is particularly effective for treatment-resistant depression. Like other more common forms of antidepressant treatment such as SSRIs, ECS has been shown to increase neurogenesis in the hippocampal dentate gyrus of rodent models. Yet the question of how ECS-induced neurogenesis supports improvement of depressive symptoms remains unknown. Here, we show that ECS-induced neurogenesis is necessary to improve depressive-like behavior of mice exposed to chronic corticosterone (Cort). We then use slice electrophysiology to show that optogenetic stimulation of adult-born neurons produces a greater hyperpolarization in mature granule neurons after ECS vs Sham treatment. We identify that this hyperpolarization requires the activation of group II metabotropic glutamate receptors. Consistent with this finding, we observe reduced expression of the immediate early gene cFos in the granule cell layer of ECS vs Sham subjects. Using single nucleus RNA sequencing, we reveal major transcriptomic shifts in granule neurons after treatment with ECS+Cort or fluoxetine+Cort vs Cort alone. We identify a population of immature cells which has greater representation in both ECS+Cort and fluoxetine+Cort treated samples vs Cort alone. We also find global differences in ECS-vs fluoxetine-induced transcriptomic shifts. Together, these findings highlight a critical role for immature granule cells in the antidepressant action of ECS.

neuroscience↗

bioRxiv2023

A tale of two receptors: simultaneous targeting of NMDARs and 5-HT4Rs exerts additive effects against stress

BACKGROUNDSerotonin (5-HT) receptors and N-methyl-D-aspartate receptors (NMDARs) have both been implicated in the pathophysiology of depression and anxiety disorders. Here, we evaluated whether targeting both receptors through combined dosing of (R,S)-ketamine, an NMDAR antagonist, and prucalopride, a serotonin type IV receptor (5-HT4R) agonist, would have additive effects, resulting in reductions in stress-induced fear, behavioral despair, and hyponeophagia. METHODSA single injection of saline (Sal), (R,S)-ketamine (K), prucalopride (P), or a combined dose of (R,S)-ketamine and prucalopride (K+P) was administered before or after contextual fear conditioning (CFC) stress in both sexes. Drug efficacy was assayed using the forced swim test (FST), elevated plus maze (EPM), open field (OF), marble burying (MB), and novelty-suppressed feeding (NSF). Patch clamp electrophysiology was used to measure the effects of combined drug on neural activity in hippocampal CA3. c-fos and parvalbumin (PV) expression in the hippocampus (HPC) and medial prefrontal cortex (mPFC) was examined using immunohistochemistry and network analysis. RESULTSWe found that a combination of K+P, given before or after stress, exerted additive effects, compared to either drug alone, in reducing a variety of stress-induced behaviors in both sexes. Combined K+P administration significantly altered c-fos and PV expression and network activity in the HPC and mPFC. CONCLUSIONSOur results indicate that combined K+P has additive benefits for combating stress-induced pathophysiology, both at the behavioral and neural level. Our findings provide preliminary evidence that future clinical studies using this combined treatment strategy may prove advantageous in protecting against a broader range of stress-induced psychiatric disorders.

neuroscience↗

bioRxiv2022

Adult born hippocampal granule cells promote pattern separation by bidirectionally modulating the remapping of place and cue cells.

The hippocampal dentate gyrus (DG) exhibits a unique form of neural plasticity that results from continuous integration of adult born neurons, referred to as adult neurogenesis. Recent studies have proposed that adult neurogenesis promotes the ability to encode new memories without interference from previously stored memories that share similar features, through a neural computation known as pattern separation. However, due to lack of in vivo physiological evidence, the manner in which adult neurogenesis contributes to pattern separation remains unknown. Here, we investigate the contribution of functionally integrated yet immature adult born granule cells (iGCs) to DG computations by examining how chronic ablation or acute chemogenetic silencing of iGCs affects the activity of mature granule cells (mGCs) using in vivo 2-photon Ca2+ imaging. In both cases we observed altered remapping of mGCs but in opposite directions depending on their tuning selectivity. Rather than broadly modulating the activity of all mGCs, iGCs promote the remapping of place cells but limit the remapping of mGCs representing sensory cues (cue cells). We propose that these properties of iGCs explain their role in pattern separation because they promote the formation of non-overlapping representations for identical sensory cues encountered in different locations. Conversely, the absence of iGCs shifts the DG network to a state dominated by sensory cue information, a situation that is consistent with the overgeneralization often observed in anxiety disorders such as PTSD.

neuroscience↗