Biology subjects

Medini, P.

Publications and source records attributed to Medini, P..

6 recordsLinked to original sources

bioRxiv2025

Anatomical input-output streams within mouse orbitofrontal cortex subdivisions

The orbitofrontal cortex (OFC) supports flexible value representation and decision making in primates, where different OFC subdivisions encode rewarding or aversive stimuli, and OFC dysfunction is implicated in depression. Recent anatomical and functional investigations have been performed in mice, but species differences in reward and value encoding physiology calls for deeper investigation of mouse OFC connectivity to better support translational research. Here, we compared density of retrograde inputs, axonal outputs and inter-subdivision connectivity, focusing on MO (medial-orbital), VO (ventral-orbital), (D)LO ((dorso)lateral-orbital) and AI (agranular insula). Central subdivisions (LO,VO) received dominant inputs from mediodorsal and submedius thalamic nuclei and projected respectively to medial prefrontal areas and sensory cortices. The striatal output was directed towards dorsal striatum, with reciprocal brainstem dopaminergic innervation. Input sources were more distributed for MO and AI, with reciprocal outputs to medial prefrontal cortices and amygdala, respectively. Striatal output was mainly to ventral striatum, and AI also received strong serotoninergic innervation. Cluster analysis revealed that VO/LO, and to lesser extent MO/DLO, shared strong similar input distributions, distinct from AI. Output clustering separated VO targeting sensory areas and AI targeting amygdala. Intra-OFC connectivity suggested information flow preferentially from (D)LO (entry nodes), to VO, MO and finally AI (output node). Together these data suggest a model that integrates in-series, information on sensory-motor plans (at (D)LO)), motivational state and cue uncertainty (at VO/LO) and current goals (at MO), via AI modulating the amygdaloidal and ventral striatal outputs, thus proposing an experimentally testable circuit to control emotional reactivity and decision-making in mouse OFC.

neuroscience↗

bioRxiv2025

Satiation is associated with OGT-dependent regulation of excitatory synapses.

Satiation is essential for energy homeostasis and is dysregulated in metabolic disorders like obesity and eating disorders such as anorexia nervosa. While satiation engages a large neural network across brain regions, how the communication within this network depends on metabolic fluctuations is unclear. This study shows that nutrient access can affect neuron-to-neuron communication in this network by regulating excitatory synaptic plasticity through O-GlcNAc transferase (OGT) in CaMKII satiation neurons in the paraventricular nucleus (PVN). Using cell-specific knockout mice and electrophysiological recordings, we demonstrate that OGT deletion in PVNCaMKII neurons increases input resistance and neuronal excitability while preserving basic membrane electrical properties. Strikingly, feeding triggered a robust 3.8-fold increase in the excitatory synaptic input in wild-type neurons, whereas OGT-knockout neurons failed to exhibit this feeding-induced synaptic activation, instead displayed a paradoxical trend towards increases in synaptic activity during hungry conditions. Furthermore, OGT deletion destabilized glucose-dependent synaptic responses, with knockout neurons displaying maladaptive depression of excitatory transmission in conditions where stability is normally preserved. These findings establish OGT as a nutrient-sensitive modulator of synaptic plasticity that ensures appropriate satiation signalling by coupling metabolic state to synaptic plasticity.

neuroscience↗

bioRxiv2025

Somatostatine interneurons mediate dopamine-dependent sensory gating in the orbitofrontal cortex

The prefrontal cortex continuously filters irrelevant stimuli, and deficits in this sensory gating predispose to psychotic disorders. In schizophrenia, the normally observed suppression of second response to two paired sounds is drastically reduced. Apart from sensitivity to critical schizophrenia players as NMDA and dopamine, the microcircuitry behind gating remains unknown. We found that the first sound excitatory response recruits, via NMDA receptors, local inhibition to gate the second response via GABAB receptors. Optogenetic inhibition of somatostatine-interneurons counteracted gating more effectively compared to parvalbumine-positive interneurons. Dopamine local blockade also counteracted gating, and dopamine effect was prevented by somatostatine-, but not parvalbumine-, optoactivation. Thus, prefrontal gating is mediated by NMDA-dependent recruitment of dendrite-targeting, somatostatine-interneurons, facilitated by dopamine. The results identify a critical synapse to better target psychose-prone disorders.

neuroscience↗

bioRxiv2024

A sequential event-responsive fluorescent reporter for inducible Cre and Flp combinatorial recombination

Current technologies for precise genetic manipulation of cells often utilize site-specific recombinases, enabling the creation of conditional transgenic models for studying gene functions in specific tissues and at defined time windows. The advent of drug-inducible recombinases has further enhanced this field by allowing temporal control of gene expression. However, detecting gene expression patterns when multiple recombinases are used is challenging, particularly when visualizing combinatorial maps and their temporal profile. To address this, we developed Rubik, a fluorescent genetic reporter specifically designed to monitor the action of Cre and Flp recombinases by expressing different fluorophores depending on the temporal sequence of recombination events. Rubik offers four alternative fluorescent configurations: blue for Cre recombination, green for Flp recombination, yellow for Cre followed by Flp recombination, and red for Flp followed by Cre recombination. Additionally, Rubik integrates light-gated ion channels, allowing optogenetic excitation or inhibition of electrically-excitable cells based on the temporal sequence of recombination events. Moreover, to add temporal control over Rubik recombination, we optimized a trimethoprim-inducible FlpO recombinase (FlpO-DD) to use in combination with the tamoxifen-inducible Cre recombinase (ERT2CreERT2). We validated Rubik by generating a stable knock-in HeLa cell line using CRISPR-Cas9 and single-cell sorting. Our results confirmed the effective functioning of Rubik with Cre and Flp recombinases and showed the ability to induce selective recombination via either tamoxifen or trimethoprim. This system holds potential for neuroscience research, particularly in generating knock-in mice expressing Rubik, which could be instrumental in precisely defining the roles of specific neuronal populations based on Cre and Flp activity.

molecular biology↗

bioRxiv2022

Multiphoton holographic photostimulation induces potassium-dependent spike silencing in label-free mouse cortex in vivo

Multiphoton microscopy allows measurement of network activity as well as the manipulation of cell type specific or functionally identified neuronal subpopulations with optogenetic holographic stimulation. When neurons co-express an activity reporter (e.g. calcium or voltage-sensitive indicators) and an (excitatory or inhibitory) opsin, such "all optical" interrogation approaches in vivo allows to draw causal links between function of cell-type specific microcircuits and behaviour. However, the net effects of near-infrared stimulation on network activity per se remain to be adequately investigated in vivo. Here we show that multicell holographic photostimulation with near-infrared radiation with total powers to sample used in current literature halves the spike rate of the non-illuminated neurons in label-free mouse cortex in vivo. The effect is not mediated by GABA release, but depends on NIR-dependent gating of potassium channels as it is absent when neurons are intracellularly perfused with the broad potassium channel blocker cesium ions, and are possibly mediated by heating. The phenomenon may contribute to set an upper limit to holographic photostimulation efficacy, calls for the need to control the effects of holographic stimulation protocols per se in label free preparations, and might be of relevance to interpret the therapeutical effects on infrared stimulation in psychiatry and neurology. Highlights- Holographic multi-cell, infrared illumination halves spike rates of no-target neurons - The effect happens with total powers to sample used in "all-optical" literature - Infrared-driven spike killing is GABA-independent but depends on potassium channels

neuroscience↗

bioRxiv2021

Visual stimulation with blue wavelength light drives V1 effectively eliminating stray light contamination during two-photon calcium imaging

BACKGROUNDBrain visual circuits are often studied in vivo by imaging Ca2+ indicators with green-shifted emission spectra. Polychromatic white visual stimuli have a spectrum that partially overlaps indicators emission spectra, resulting in significant contamination of calcium signals. NEW METHODTo overcome light contamination problems we choose blue visual stimuli, having a spectral composition not overlapping with Ca2+ indicators emission spectrum. To compare visual responsiveness to blue and white stimuli we used electrophysiology (visual evoked potentials-VEPs) and 3D acousto-optic two-photon(2P) population Ca2+ imaging in mouse primary visual cortex (V1). RESULTSVEPs in response to blue and white stimuli had comparable peak amplitudes and latencies. Ca2+ imaging revealed that the populations of neurons responding to blue and white stimuli were largely overlapping, that their responses had similar amplitudes, and that functional response properties such as orientation and direction selectivities were also comparable. COMPARISON WITH EXISTING METHODSMasking or shielding the microscope are often used to minimize the contamination of Ca2+ signal by white light, but they are time consuming, bulky and thus can limit experimental design, particularly in the more and more frequently used awake set-up. Blue stimuli not interfering with imaging allow to omit shielding without affecting V1 physiological responsiveness. CONCLUSIONSOur results show that the selected blue light stimuli evoke physiological responses comparable to those evoked by white stimuli in mouse V1. This will make complex designs of imaging experiments in behavioral set-ups easier, and facilitate the combination of Ca2+ imaging with electrophysiology and optogenetics. HighlightsO_LIWhite and blue light trigger VEPs with similar amplitudes and latencies in mouse V1 C_LIO_LIBlue-and white-responding neurons are two largely overlapping neuronal populations C_LIO_LIBlue and white evoke Ca2+ responses similar in magnitude and latency C_LIO_LIBlue and white evoke Ca2+ responses similar in orientation/direction selectivity C_LIO_LIBlue stimuli could be an alternative to white ones in behavior and opto-physiological tests C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=149 SRC="FIGDIR/small/433182v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@66c0a2org.highwire.dtl.DTLVardef@1f0cce9org.highwire.dtl.DTLVardef@1ce97borg.highwire.dtl.DTLVardef@24a3f1_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗