Superresolution Imaging of Cytoskeletal Networks in Fixed Brain Tissue.

Emerging evidence suggests that neurodegeneration is directly linked to dysfunction of cytoskeleton; however, visualizing the organization of cytoskeletal structures in brain tissues remains challenging due to the limitation of resolution of light microscopy. Superresolution imaging overcomes this limitation and resolves subcellular structures below the diffraction barrier of light (20-200 nm), while retaining the advantages of fluorescent microscopy such as simultaneous visualization of multiple proteins and increased signal sensitivity and contrast. However, superresolution imaging approaches have been largely limited to very thin samples such as cultured cells growing as a single monolayer.

Anatomical Organization of the Rat Subfornical Organ.

The subfornical organ (SFO) is a sensory circumventricular organ located along the anterodorsal wall of the third ventricle. SFO lacks a complete blood-brain barrier (BBB), and thus peripherally-circulating factors can penetrate the SFO parenchyma. These signals are detected by local neurons providing the brain with information from the periphery to mediate central responses to humoral signals and physiological stressors.

High dietary salt amplifies osmoresponsiveness in vasopressin-releasing neurons.

High dietary salt increases arterial pressure partly through activation of magnocellular neurosecretory cells (MNC) that secrete the antidiuretic and vasoconstrictor hormone vasopressin (VP) into the circulation. Here, we show that the intrinsic and synaptic excitation of MNC caused by hypertonicity are differentially potentiated in two models of salt-dependent hypertension in rats. One model combined salty chow with a chronic subpressor dose of angiotensin II (AngII-salt), the other involved replacing drinking water with 2% NaCl (salt loading, SL).

Unique Organization of Actin Cytoskeleton in Magnocellular Vasopressin Neurons in Normal Conditions and in Response to Salt-Loading.

Magnocellular neurosecretory cells (MNCs) are intrinsically osmosensitive and can be activated by increases in blood osmolality, triggering the release of antidiuretic hormone vasopressin (VP) to promote water retention. Hence, the activity of magnocellular VP neurons is one of the key elements contributing to the regulation of body fluid homeostasis in healthy organisms. Chronic exposure to high dietary salt leads to excessive activation of VP neurons, thereby elevating levels of circulating VP, which can cause increases in blood pressure contributing to salt-dependent hypertension.

Effects of salt loading on the organisation of microtubules in rat magnocellular vasopressin neurones.

Magnocellular vasopressin (VP) neurones are activated by increases in blood osmolality, leading to the secretion of VP into the circulation to promote water retention in the kidney, thus constituting a key mechanism for the regulation of body fluid homeostasis. However, chronic high salt intake can lead to excessive activation of VP neurones and increased circulating levels of VP, contributing to an elevation in blood pressure. Multiple extrinsic factors, such as synaptic inputs and glial cells, modulate the activity of VP neurones.