Axonal Control of the Adult Neural Stem Cell Niche

SUMMARYThe ventricular-subventricular zone (V-SVZ) is an extensive germinal niche containing neural stem cells (NSC) in the walls of the lateral ventricles of the adult brain. How the adult brain’s neural activity influences the behavior of adult NSCs remains largely unknown. We show that serotonergic (5HT) axons originating from a small group of neurons in the raphe form an extensive plexus on most of the ventricular walls. Electron microscopy revealed intimate contacts between 5HT axons and NSCs (B1) or ependymal cells (E1) and these cells were labeled by a transsynaptic viral tracer injected into the raphe. B1 cells express the 5HT receptors 2C and 5A. Electrophysiology showed that activation of these receptors in B1 cells induced small inward currents. Intraventricular infusion of 5HT2C agonist or antagonist increased or decreased V-SVZ proliferation, respectively. These results indicate that supraependymal 5HT axons directly interact with NSCs to regulate neurogenesis via 5HT2C

An optimized iDISCO+ protocol for tissue clearing and 3D analysis of oxytocin and vasopressin cell network in the developing mouse brain

Summary: Here, we present an optimized iDISCO+ protocol combining tissue clearing and light sheet microscopy to map the postnatal development of oxytocin and vasopressin neurons in mouse hypothalamus. We describe tissue preparation, immunostaining, clearing, and imaging. We then detail how to process the 3D cell dataset to analyze cell network using a point-based recording procedure that accurately maps neurons in the Allen brain atlas. This protocol can be applied to any neuronal population, in different brain regions and at different developmental stages.For complete details on the use and execution of this protocol, please refer to Soumier et al. (2021).1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics

Dépression et neuroplasticité : implication des systèmes sérotoninergiques

L'analyse des effets des antidépresseurs sur la neuroplasticité, et plus particulièrement sur la formation de nouveaux neurones dans le cerveau adulte, constitue aujourd'hui un thème de recherche novateur compte tenu de l'implication d'une modification de la connectivité neuronale dans la physiopathologie des troubles de l'humeur. Les modèles animaux de stress chronique ont permis de révéler des altérations structurales au niveau de l'hippocampe notamment, qui sont réversibles avec le temps et les traitements antidépresseurs. Chez des patients atteints de dépression majeure, on observe aussi une diminution du volume hippocampique qui a été associée à des déficits cognitifs. Dans ce contexte, la sérotonine (5-HT) apparaît jouer un rôle clé, par ses effets notables dans la réponse au stress et le traitement de la dépression, comme dans son implication dans les processus de la neuroplasticité et sa faculté de stimuler la neurogenèse secondaire. D'autres antidépresseurs, comme l'agomélatine ayant des propriétés à la fois sérotoninergique et mélatoninergique, entraînent aussi une augmentation de ce processus, et bien que ces observations ne permettent pas pour l'instant de proposer un mécanisme sous-jacent commun à l'ensemble de ces effets, leurs conséquences pourraient avoir une implication importante dans le traitement des troubles de l'humeur

Region- and phase-dependent effects of 5-HT(1A) and 5-HT(2C) receptor activation on adult neurogenesis.

International audienceAdult neurogenesis and serotoninergic transmission are associated to mood disorders and their treatments. The present study focused on the effects of chronic activation of 5-HT(1A) and 5-HT(2C) receptors on newborn cell survival in the dentate gyrus (DG) and olfactory bulb (OB), and examined whether potential neurogenic zones as the prefrontal cortex (PFC) and striatum (ST) are reactive to these treatments. Administration of 8-OH-DPAT, but not RO600,175 increases neurogenesis and survival of late differentiating cells (15-21days) in the DG. Both 8-OH-DPAT and RO600,175 increase neurogenesis in the OB, but only 8-OH-DPAT affected cell survival, inducing a parallel decrease in the number of BrdU cells in the OB and increase in the SVZ, which suggests an impaired migration. In the PFC and ST, 8-OH-DPAT and R0600,175 increase gliogenesis (NG2-labeled cells). This study provides new insights on the serotonergic regulation of critical phases of neurogenesis helpful to understand the neurogenic and gliogenic effects of antidepressant treatments in different brain regions

Stress can increase or decrease anxiety depending on the timing of the stressor

<p>The purpose of these experiments was to determine the immediate and delayed effects of stress on anxiety/depressive behavior. For the open field and elevated plus maze experiments male CD1 mice (Charles River) were used (n=6-8 per group; arrived at 7 weeks of age, tested at 9-11 weeks, handled for 5 days prior to testing). The GFAP-tk mice used for the novelty-suppressed feeding test were as described in Snyder, 2011, Nature. Mice were housed 4/cage, kept on a 12 hour light/dark cycle with lights on at 6 am and were tested during the light phase. Testing was performed either directly from the home cage (controls), immediately following 30 min restraint (stress) or following 30 min restraint with a 30 min post-restraint delay interval (stress+delay).</p> <p>Figure 1: Increased fear/anxiety in the open field immediately following stress. a) The open field was a white plastic box (50cm x 50cm x 50cm) which was divided into outer (o), middle (m), and center (c) regions. Mice were tracked with Ethovision software (Noldus) and latency to approach the center region and time spent in the 3 regions during a 15 min test was calculated. Light intensity was approximately 150 lux. b) The presence of an object (~2 cm diameter, 3 cm tall wire metal cylinder containing a marble) in the center of the open field increased time spent in this subregion, and was therefore included in subsequent experiments (i.e. d-h; ****t-test P</p> <p>Figure 2: Reduced fear/anxiety in the elevated plus maze 30 min after stress. Mice were subjected to a 5 min test in the EPM under bright (~150 lux; a-g) and dark (15 lux; h-n) conditions. The EPM had two open arms and two opaque closed arms and was located in the center of the testing room. a) Stress+delay increased the amount of time spent in the open arm during the first 2.5 min of the test (bin 1; *t-test, P</p> <p>In sum, stress can increase anxiety immediately after termination of the stressor: stressed mice spent less time than controls in the center of the open field. Stress can also reduce anxiety at later times after termination of the stressor: stress+delay mice spent more time in the open arms of the elevated plus maze, stress+delay mice displayed more head dipping behavior in the elevated plus maze, and stress+delay mice ate sooner in the novelty- suppressed feeding test. Also, in the open field, 1/3 of mice in the control and stress groups did not approach the center until 4+ min had elapsed. In contrast, though not significantly different, there was less variability in the stress+delay mice with all approaching the center by ~2 min, consistent with the possibility that stress+delay is reducing anxiety in some of these mice.</p

Selective effect of agomelatine treatment on ventral hippocampal neurogenesis in the rat model of prenatal restraint stress: Implications for anxiety behavior

DecretOANoAutActifinfo:eu-repo/semantics/inPres