Impaired dynamics of precapillary sphincters and pericytes at first-order capillaries predict reduced neurovascular function in the aging mouse brain.

The microvascular inflow tract, comprising the penetrating arterioles, precapillary sphincters and first-order capillaries, is the bottleneck for brain blood flow and energy supply. Exactly how aging alters the structure and function of the microvascular inflow tract remains unclear. By in vivo four-dimensional two-photon imaging, we reveal an age-dependent decrease in vaso-responsivity accompanied by a decrease in vessel density close to the arterioles and loss of vascular mural cell processes, although the number of mural cell somas and their alpha smooth muscle actin density were preserved.

Modification of oxygen consumption and blood flow in mouse somatosensory cortex by cell-type-specific neuronal activity.

Gamma activity arising from the interplay between pyramidal neurons and fast-spiking parvalbumin (PV) interneurons is an integral part of higher cognitive functions and is assumed to contribute significantly to brain metabolic responses. Cerebral metabolic rate of oxygen (CMRO) responses were evoked by optogenetic stimulation of cortical PV interneurons and pyramidal neurons. We found that CMRO responses depended on neuronal activation, but not on the power of gamma activity induced by optogenetic stimulation.

Sensory Stimulation-Induced Astrocytic Calcium Signaling in Electrically Silent Ischemic Penumbra.

Middle cerebral artery occlusion (MCAO) induces ischemia characterized by a densely ischemic focus, and a less densely ischemic penumbral zone in which neurons and astrocytes display age-dependent dynamic variations in spontaneous Ca activities. However, it is unknown whether penumbral nerve cells respond to sensory stimulation early after stroke onset, which is critical for understanding stimulation-induced stroke therapy. In this study, we investigated the ischemic penumbra's capacity to respond to somatosensory input.

In Vivo Three-Dimensional Two-Photon Microscopy to Study Conducted Vascular Responses by Local ATP Ejection Using a Glass Micro-Pipette.

Maintenance of normal brain function requires a sufficient and efficient supply of oxygen and nutrition by a complex network of vessels. However, the regulation of cerebral blood flow (CBF) is incompletely understood, especially at the capillary level. Two-photon microscopy is a powerful tool widely used to study CBF and its regulation.

Continuous EEG Monitoring in a Consecutive Patient Cohort with Sepsis and Delirium.

Background: Delirium is common during sepsis, although under-recognized. We aimed to assess the value of continuous electroencephalography (cEEG) to aid in the diagnosis of delirium in septic patients.

Methods: We prospectively evaluated 102 consecutive patients in a medical intensive care unit (ICU), who had sepsis or septic shock, without evidence of acute primary central nervous system disease.

Spontaneous astrocytic Ca activity abounds in electrically suppressed ischemic penumbra of aged mice.

Experimental focal cortical ischemic lesions consist of an ischemic core and a potentially salvageable peri-ischemic region, the ischemic penumbra. The activity of neurons and astrocytes is assumed to be suppressed in the penumbra because the electrical function is interrupted, but this is incompletely elucidated. Most experimental stroke studies used young adult animals, whereas stroke is prevalent in the elderly population.

Neuronal inhibition and excitation, and the dichotomic control of brain hemodynamic and oxygen responses.

Brain's electrical activity correlates strongly to changes in cerebral blood flow (CBF) and the cerebral metabolic rate of oxygen (CMRO(2)). Subthreshold synaptic processes correlate better than the spike rates of principal neurons to CBF, CMRO(2) and positive BOLD signals. Stimulation-induced rises in CMRO(2) are controlled by the ATP turnover, which depends on the energy used to fuel the Na,K-ATPase to reestablish ionic gradients, while stimulation-induced CBF responses to a large extent are controlled by mechanisms that depend on Ca(2+) rises in neurons and astrocytes.

Nonlinear neurovascular coupling in rat sensory cortex by activation of transcallosal fibers.

Functional neuroimaging and normal brain function rely on the robust coupling between neural activity and cerebral blood flow (CBF), that is neurovascular coupling. We examined neurovascular coupling in rat sensory cortex in response to direct stimulation of transcallosal pathways, which allows examination of brain regions inaccessible to peripheral stimulation techniques. Using laser-Doppler flowmetry to record CBF and electrophysiologic recordings of local field potentials (LFPs), we show an exponential relation between CBF responses and summed LFP amplitudes.