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.

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.

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.

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.

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.

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)).

Using mouse olfactory bulb as a model system we compare the performance of genetically-encoded calcium sensor TN-XXL and small molecule calcium indicators; describe how to choose the right calcium indicator and how to load it into the cells of interest; discuss the use of cell type-specific markers and, finally, illustrate the application of this technique for high resolution in vivo imaging of sensory-driven neuronal activity.

In the healthy adult brain microglia, the main im­mune-com­pe­tent cells of the CNS, have a dis­tinct (so-called “rest­ing”, see image) phe­notype. Rest­ing microglia can only be stud­ied in vivo since any isolation of brain tissue inevitably trig­gers microglial activation. Us­ing in vivo two-photon imag­ing we obtained a first di­rect in­sight into Ca²⁺ signaling in rest­ing cortical microglia.