Juxtaglomerular neurons (JGNs) of the mammalian olfactory bulb are generated throughout life. Their integration into the preexisting neural network, their differentiation and survival therein depend on sensory activity, but when and how these adult-born cells acquire responsiveness to sensory stimuli remains unknown. In vivo two-photon imaging of retrovirally labelled adult-born JGNs reveals that ~90% of the cells arrive at the glomerular layer after day post injection (DPI) 7. After arrival, adult-born JGNs are still migrating, but at DPI 9, 52% of them have odour-evoked Ca(2+) signals. Their odourant sensitivity closely resembles that of the parent glomerulus and surrounding JGNs, and their spontaneous and odour-evoked spiking is similar to that of their resident neighbours.

The dynamics of β-amyloid deposition and related second-order physiological effects, such as regional cerebral blood flow (rCBF), are key factors for a deeper understanding of Alzheimer's disease (AD). We present longitudinal in vivo data on the dynamics of β-amyloid deposition and the decline of rCBF in two different amyloid precursor protein (APP) transgenic mouse models of AD. Using a multiparametric positron emission tomography and magnetic resonance imaging approach, we demonstrate that in the presence of cerebral β-amyloid angiopathy (CAA), β-amyloid deposition is accompanied by a decline of rCBF. Loss of perfusion correlates with the growth of β-amyloid plaque burden but is not related to the number of CAA-induced microhemorrhages.

Neuroinflammation is a hallmark of Alzheimer’s disease (AD) both in man and in multiple mouse models, and epidemiological studies link the use of anti-inflammatory drugs with a reduced risk of developing the disease. AD-related neuroinflammation is largely mediated by microglia, the main immune cells of the central nervous system. In vitro, executive functions of microglia are regulated by intracellular Ca2+ signals, but little is known about microglial Ca2+ signaling in vivo. Here we analyze in vivo properties of these cells in two mouse models of AD. In both strains plaque-associated microglia had hypertrophic/amoeboid morphology and were strongly positive for markers of activation such as CD11b and CD68.

The quality of genetically encoded calcium indicators (GECIs) has improved dramatically in recent years, but high-performing ratiometric indicators are still rare. Here we describe a series of fluorescence resonance energy transfer (FRET)-based calcium biosensors with a reduced number of calcium binding sites per sensor. These 'Twitch' sensors are based on the C-terminal domain of Opsanus troponin C. Their FRET responses were optimized by a large-scale functional screen in bacterial colonies, refined by a secondary screen in rat hippocampal neuron cultures. We tested the in vivo performance of the most sensitive variants in the brain and lymph nodes of mice.

Dysregulation of intracellular Ca2+ homeostasis has been proposed as a common proximal cause of neural dysfunction during aging and Alzheimer's disease (AD). In this context, aberrant Ca2+ signaling has been viewed as a neuronal phenomenon mostly related to the dysfunction of intracellular Ca2+ stores. However, recent data suggest that, in AD, Ca2+ dyshomeostasis is not restricted to neurons but represents a global phenomenon affecting virtually all cells in the brain. AD-related aberrant Ca2+ signaling in astrocytes and microglia, which is activated during the disease, probably contributes profoundly to an inflammatory response that, in turn, impacts neuronal Ca2+ homeostasis and brain function.

Juxtaglomerular neurons represent one of the largest cellular populations in the mammalian olfactory bulb yet their role for signal processing remains unclear. We used two-photon imaging and electrophysiological recordings to clarify the in vivo properties of these cells and their functional organization in the juxtaglomerular space. Juxtaglomerular neurons coded for many perceptual characteristics of the olfactory stimulus such as (1) identity of the odorant, (2) odorant concentration, (3) odorant onset, and (4) offset.

Microglial cells are the resident immune cells of the CNS. They mediate innate immune response of the brain to injury, inflammation and neurodegenerative diseases. Apart from their role in disease they are critically involved in the development and plasticity-driven reorganization of neuronal networks and the homeostatic maintenance of brain tissue.

Under most physiological   circumstances, monocytes are excluded from parenchymal CNS tissues. When widespread monocyte entry occurs, their numbers decrease shortly after engraftment in the presence of microglia. However, some disease processes lead to focal and selective loss, or dysfunction, of microglia, and microglial senescence typifies the aged brain. In this regard, the long-term engraftment of monocytes in the microglia-depleted brain remains unknown. Here, we report a model in which a niche for myeloid cells was created through microglia depletion. We show that microglia-depleted brain regions of CD11b-HSVTK transgenic mice are repopulated with new Iba-1-positive cells within 2 wk.

We describe a technique utilizing Tomato lectin conjugated with green or red fluorescent dye for fast and reliable in vivo labeling of microglia. This protocol enables high resolution imaging of microglial cells in wild type/mutant mice of any age, and in mouse models of Alzheimer’s disease. The labeling does not disturb the functional properties of microglia or the surrounding neurons and is preserved in fixed tissue used for post-hoc immunostaining.

See more: http://www.ncbi.nlm.nih.gov/pubmed/22622946

SR101 turned out to be a highly bioactive molecule. When tested in acutely prepared hippocampal slices this substance markedly increased the excitability of neuronal tissue (Fig. 1B-F, (Fink et al., 2011)). Bath application of SR101 induced a 5-6 fold increase in the amplitude of a synaptically-evoked population spike caused by the stimulation of Schaffer collaterals and provoked a synchronized repetitive firing of neurons at a frequency of 130-200 Hz. The SR101-evoked hyperexcitability developed rapidly (the maximal effect was reached during the first 5 min of drug application) and persisted for at least 40-60 min after the wash-out of the drug. Field EPSPs recorded in the stratum radiatum of the CA1 region also underwent long lasting potentiation.