A neuronal circuit driven by GLP-1 in the olfactory bulb regulates insulin secretion.

Glucagon-like peptide 1 (GLP-1) stimulates insulin secretion and holds significant pharmacological potential. Nevertheless, the regulation of energy homeostasis by centrally-produced GLP-1 remains partially understood. Preproglucagon cells, known to release GLP-1, are found in the olfactory bulb (OB).

Design and validation of a convolutional neural network for fast, model-free blood flow imaging with multiple exposure speckle imaging.

Multiple exposure speckle imaging has demonstrated its improved accuracy compared to single exposure speckle imaging for relative quantitation of blood flow . However, the calculation of blood flow maps relies on a pixelwise non-linear fit of a multi-parametric model to the speckle contrasts. This approach has two major drawbacks.

The local GLP-1 system in the olfactory bulb is required for odor-evoked cephalic phase of insulin release in mice.

Objective: The olfactory bulb (OB) codes for sensory information and contributes to the control of energy metabolism by regulating foraging and cephalic phase responses. Mitral cells are the main output neurons of the OB. The glucagon-like peptide-1 (GLP-1)/GLP-1 receptor (GLP-1R) system in the OB (GLP-1) has been shown to be a major regulator of mitral cell activity but its function in vivo is unclear.

Olfaction in the context of obesity and diabetes: Insights from animal models to humans.

The olfactory system is at the crossroad between sensory processing and metabolic sensing. In addition to being the center of detection and identification of food odors, it is a sensor for most of the hormones and nutrients responsible for feeding behavior regulation. The consequences of modifications in body homeostasis, nutrient overload and alteration of this brain network in the pathological condition of food-induced obesity and type 2 diabetes are still not elucidated.

Correction: Olfactory Training and Visual Stimulation Assisted by a Web Application for Patients With Persistent Olfactory Dysfunction After SARS-CoV-2 Infection: Observational Study.

[This corrects the article DOI: 10.2196/29583.].

Olfactory Training and Visual Stimulation Assisted by a Web Application for Patients With Persistent Olfactory Dysfunction After SARS-CoV-2 Infection: Observational Study.

Background: Persistent olfactory dysfunction is a significant complication of SARS-CoV-2 infection. Olfactory training involving aromatic oils has been recommended to improve olfactory recovery, but quantitative data are missing.

Objective: We aimed to quantify the benefit of olfactory training and visual stimulation assisted by a dedicated web application for patients who experienced olfactory dysfunction for ≥1 month.

Obesity in Midlife Hampers Resting and Sensory-Evoked Cerebral Blood Flow in Mice.

Objective: This study aimed to investigate the effects of a high-fat diet (HFD) and aging on resting and activity-dependent cerebral blood flow (CBF).

Methods: To run a comparison between obese and age-matched control animals, 6-week-old mice were fed either with regular chow or an HFD for 3 months or 8 months. Glucose tolerance and insulin sensitivity were assessed for metabolic phenotyping.

New roles for prokineticin 2 in feeding behavior, insulin resistance and type 2 diabetes: Studies in mice and humans.

Objective: Prokineticin 2 (PROK2) is a hypothalamic neuropeptide that plays a critical role in the rhythmicity of physiological functions and inhibits food intake. PROK2 is also expressed in the main olfactory bulb (MOB) as an essential factor for neuro-and morphogenesis. Since the MOB was shown to be strongly involved in eating behavior, we hypothesized that PROK2 could be a new target in the regulation of food intake and energy homeostasis, through its effects in the MOB.

Multisensory learning between odor and sound enhances beta oscillations.

Multisensory interactions are essential to make sense of the environment by transforming the mosaic of sensory inputs received by the organism into a unified perception. Brain rhythms allow coherent processing within areas or between distant brain regions and could thus be instrumental in functionally connecting remote brain areas in the context of multisensory interactions. Still, odor and sound processing relate to two sensory systems with specific anatomofunctional characteristics.

Multiple speckle exposure imaging for the study of blood flow changes induced by functional activation of barrel cortex and olfactory bulb in mice.

Speckle contrast imaging allows imaging of relative blood flow changes. Multiple exposure speckle imaging (MESI) is more accurate than the standard single-exposure method since it allows separating the contribution of the static and moving scatters of the recorded speckle patterns. MESI requires experimental validation on phantoms prior to experiments to ensure the proper calibration of the system and the robustness of the model.

Odor-Induced Neuronal Rhythms in the Olfactory Bulb Are Profoundly Modified in ob/ob Obese Mice.

Leptin, the product of the Ob(Lep) gene, is a peptide hormone that plays a major role in maintaining the balance between food intake and energy expenditure. In the brain, leptin receptors are expressed by hypothalamic cells but also in the olfactory bulb, the first central structure coding for odors, suggesting a precise function of this hormone in odor-evoked activities. Although olfaction plays a key role in feeding behavior, the ability of the olfactory bulb to integrate the energy-related signal leptin is still missing.

Functional ultrasound imaging reveals different odor-evoked patterns of vascular activity in the main olfactory bulb and the anterior piriform cortex.

Topographic representation of the outside world is a key feature of sensory systems, but so far it has been difficult to define how the activity pattern of the olfactory information is distributed at successive stages in the olfactory system. We studied odor-evoked activation patterns in the main olfactory bulb and the anterior piriform cortex of rats using functional ultrasound (fUS) imaging. fUS imaging is based on the use of ultrafast ultrasound scanners and detects variations in the local blood volume during brain activation.

The endocannabinoid system controls food intake via olfactory processes.

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).

Anesthetic regimes modulate the temporal dynamics of local field potential in the mouse olfactory bulb.

Anesthetized preparations have been widely used to study odor-induced temporal dynamics in the olfactory bulb. Although numerous recent data of single-cell recording or imaging in the olfactory bulb have employed ketamine cocktails, their effects on networks activities are still poorly understood, and odor-induced oscillations of the local field potential have not been characterized under these anesthetics. Our study aimed at describing the impact of two ketamine cocktails on oscillations and comparing them to awake condition.

Multispectral reflectance imaging of brain activation in rodents: methodological study of the differential path length estimations and first in vivo recordings in the rat olfactory bulb.

Dynamic maps of relative changes in blood volume and oxygenation following brain activation are obtained using multispectral reflectance imaging. The technique relies on optical absorption modifications linked to hemodynamic changes. The relative variation of hemodynamic parameters can be quantified using the modified Beer-Lambert Law if changes in reflected light intensities are recorded at two wavelengths or more and the differential path length (DP) is known.

Reconstruction of field excitatory post-synaptic potentials in the dentate gyrus from amperometric biosensor signals.

A new feasible and reproducible method to reconstruct local field potentials from amperometric biosensor signals is presented. It is based on the least-square fit of the current response of the biosensor electrode to a voltage step by the use of two time constants. After determination of the electrode impedance, Fast Fourier Transform (FFT) and Inverse FFT are performed to convert the recorded amperometric signals into voltage and trace the local field potentials using a resistor-capacitor circuit-based model.

Alteration of sensory-evoked metabolic and oscillatory activities in the olfactory bulb of GLAST-deficient mice.

Astrocytes are key cellular elements in both the tripartite synapse and the neurovascular unit. To fulfill this dual role in synaptic activity and metabolism, they express a panel of receptors and transporters that sense glutamate. Among them, the GLT-1 and GLAST transporters are known to regulate extracellular glutamate concentrations at excitatory synapses and consequently modulate glutamate receptor signaling.

In vivo detection of excitotoxicity by manganese-enhanced MRI: comparison with physiological stimulation.

Manganese-enhanced MRI (MEMRI) is a powerful technique for the in vivo monitoring of brain function in animals. Manganese enters into cells through calcium channels, i.e.

Imaging odor-evoked activities in the mouse olfactory bulb using optical reflectance and autofluorescence signals.

In the brain, sensory stimulation activates distributed populations of neurons among functional modules which participate to the coding of the stimulus. Functional optical imaging techniques are advantageous to visualize the activation of these modules in sensory cortices with high spatial resolution. In this context, endogenous optical signals that arise from molecular mechanisms linked to neuroenergetics are valuable sources of contrast to record spatial maps of sensory stimuli over wide fields in the rodent brain.

Visualizing odor representation in the brain: a review of imaging techniques for the mapping of sensory activity in the olfactory glomeruli.

The brain transforms clues from the external world, the sensory stimuli, into activities in neuroglial networks. These circuits are activated in specialized sensory cortices where specific functional modules are responsible for the spatiotemporal coding of the stimulus. A major challenge in the neuroscience field has been to image the spatial distribution and follow the temporal dynamics of the activation of such large populations in vivo.

Autofluorescence imaging of NADH and flavoproteins in the rat brain: insights from Monte Carlo simulations.

There has been recently a renewed interest in using Autofluorescence imaging (AF) of NADH and flavoproteins (Fp) to map brain activity in cortical areas. The recording of these cellular signals provides complementary information to intrinsic optical imaging based on hemodynamic changes. However, which of NADH or Fp is the best candidate for AF functional imaging is not established, and the temporal profile of AF signals is not fully understood.

A method based on Monte Carlo simulations and voxelized anatomical atlases to evaluate and correct uncertainties on radiotracer accumulation quantitation in beta microprobe studies in the rat brain.

The beta-microprobe is a simple and versatile technique complementary to small animal positron emission tomography (PET). It relies on local measurements of the concentration of positron-labeled molecules. So far, it has been successfully used in anesthetized rats for pharmacokinetics experiments and for the study of brain energetic metabolism.

The potential of a radiosensitive intracerebral probe to monitor 18F-MPPF binding in mouse hippocampus in vivo.

Unlabelled: As mouse imaging has become more challenging in preclinical research, efforts have been made to develop dedicated PET systems. Although these systems are currently used for the study of physiopathologic murine models, they present some drawbacks for brain studies, including a low temporal resolution that limits the pharmacokinetic study of radiotracers. The aim of this study was to demonstrate the ability of a radiosensitive intracerebral probe to measure the binding of a radiotracer in the mouse brain in vivo.