Life and Death Decision in Adult Neurogenesis: In Praise of Napping

Among the thousands of new neurons that integrate into the adult olfactory bulb each day, 50% are eliminated through apoptosis. In this issue of Neuron, Yokoyama et al. take steps toward deciphering the behavioral contexts that regulate newborn cell elimination

The endocannabinoid system controls food intake via olfactory processes

Comment in Sensory systems: the hungry sense. [Nat Rev Neurosci. 2014] Inhaling: endocannabinoids and food intake. [Nat Neurosci. 2014]; International audience; Hunger arouses sensory perception, eventually leading to an increase in food intake, but the underlying mechanisms remain poorly understood. We found that cannabinoid type-1 (CB1) receptors promote food intake in fasted mice by increasing odor detection. CB1 receptors were abundantly expressed on axon terminals of centrifugal cortical glutamatergic neurons that project to inhibitory granule cells of the main olfactory bulb (MOB). Local pharmacological and genetic manipulations revealed that endocannabinoids and exogenous cannabinoids increased odor detection and food intake in fasted mice by decreasing excitatory drive from olfactory cortex areas to the MOB. Consistently, cannabinoid agonists dampened in vivo optogenetically stimulated excitatory transmission in the same circuit. Our data indicate that cortical feedback projections to the MOB crucially regulate food intake via CB1 receptor signaling, linking the feeling of hunger to stronger odor processing. Thus, CB1 receptor-dependent control of cortical feedback projections in olfactory circuits couples internal states to perception and behavior

Physiologie de la somatostatine dans le bulbe olfactif de souris (des interneurones somatostatinergiques à la modulation du comportement olfactif)

Le neuropeptide somatostatine est largement exprimé dans le cerveau et son rôle modulateur via ses six récepteurs est bien établi dans les fonctions neuroendocriniennes et cognitives. La présence de la somatostatine et de ses récepteurs dans le système olfactif, et leur déclin dans plusieurs maladies neurodégénératives associées à des troubles précoces du sens de l odorat, suggèrent que ce peptide participe au traitement de l information olfactive. Notre travail démontre que, dans le bulbe olfactif de souris, la somatostatine est exprimée par des interneurones de van Gehuchten précisément situés dans la partie interne de la couche plexiforme externe. Ces interneurones sans axone établissent des synapses dendrodendritiques réciproques avec les dendrites latérales des cellules de projection du bulbe, les cellules mitrales. En agissant sur les récepteurs sst2 exprimés par leurs dendrites, la somatostatine influence la transmission synaptique dendrodendritique entre cellules principales et cellules granulaires qui est l origine d oscillations gamma dans le réseau neuronal bulbaire (40-100 Hz). Les variations de la puissance de ces oscillations induites par le blocage ou l activation du récepteur sst2 sont associées à des modifications du seuil de discrimination olfactive. Ainsi, nos résultats démontrent que la libération endogène de somatostatine participe à la modulation des oscillations gamma bulbaires et à la discrimination olfactive. Ce travail ouvre donc des perspectives sur l implication de la somatostatine dans le traitement de l information sensorielle et dans le fonctionnement des réseaux neuronaux du télencéphale.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Adult neurogenesis and the future of the rejuvenating brain circuits.

International audienceFor a long time, the mammalian brain has been perceived to be a static organ. However, the discovery of adult neurogenesis in most mammalian species, including humans, monkeys, and rodents, has disrupted this view. As this continuous regeneration has an effect on established behavioral patterns, it holds promising therapeutic potential. However, before harnessing this potential regenerative power, we must understand what effects new neurons have on existing brain circuits. Ongoing research contributes to several important steps toward bridging the gap between adult-born neurons, circuits, and behavior. The study of adult neurogenesis in different neurogenic regions from a systems neuroscience perspective will pave the way to understanding how it supports adaptive behavior and why its dysfunction correlates with some human brain disorders

Anticorps et procédés de traitement d'une infection par lyssavirus

The invention provides antibodies, and antigen-binding fragments thereof, that potently neutralize lyssavirus infection and the use of such antibodies. In particular, the invention provides methods of treatment of lyssavirus infection, such as rabies.L'invention concerne des anticorps et des fragments de liaison à l'antigène de ceux-ci, qui neutralisent puissamment l'infection par lyssavirus, ainsi que l'utilisation de tels anticorps. En particulier, l'invention concerne des procédés de traitement d'une infection par lyssavirus, telle que la rage

GABAB Receptors Tune Cortical Feedback to the Olfactory Bulb.

International audienceSensory perception emerges from the confluence of sensory inputs that encode the composition of external environment and top-down feedback that conveys information from higher brain centers. In olfaction, sensory input activity is initially processed in the olfactory bulb (OB), serving as the first central relay before being transferred to the olfactory cortex. In addition, the OB receives dense connectivity from feedback projections, so the OB has the capacity to implement a wide array of sensory neuronal computation. However, little is known about the impact and the regulation of this cortical feedback. Here, we describe a novel mechanism to gate glutamatergic feedback selectively from the anterior olfactory cortex (AOC) to the OB. Combining in vitro and in vivo electrophysiological recordings, optogenetics, and fiber-photometry-based calcium imaging applied to wild-type and conditional transgenic mice, we explore the functional consequences of circuit-specific GABA type-B receptor (GABABR) manipulation. We found that activation of presynaptic GABABRs specifically depresses synaptic transmission from the AOC to OB inhibitory interneurons, but spares direct excitation to principal neurons. As a consequence, feedforward inhibition of spontaneous and odor-evoked activity of principal neurons is diminished. We also show that tunable cortico-bulbar feedback is critical for generating beta, but not gamma, OB oscillations. Together, these results show that GABABRs on cortico-bulbar afferents gate excitatory transmission in a target-specific manner and thus shape how the OB integrates sensory inputs and top-down information

Selective viral transduction of adult-born olfactory neurons for chronic in vivo optogenetic stimulation.

International audienceLocal interneurons are continuously regenerated in the olfactory bulb of adult rodents. In this process, called adult neurogenesis, neural stem cells in the walls of the lateral ventricle give rise to neuroblasts that migrate for several millimeters along the rostral migratory stream (RMS) to reach and incorporate into the olfactory bulb. To study the different steps and the impact of adult-born neuron integration into preexisting olfactory circuits, it is necessary to selectively label and manipulate the activity of this specific population of neurons. The recent development of optogenetic technologies offers the opportunity to use light to precisely activate this specific cohort of neurons without affecting surrounding neurons. Here, we present a series of procedures to virally express Channelrhodopsin2(ChR2)-YFP in a temporally restricted cohort of neuroblasts in the RMS before they reach the olfactory bulb and become adult-born neurons. In addition, we show how to implant and calibrate a miniature LED for chronic in vivo stimulation of ChR2-expressing neurons