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Deciphering the Neuronal Circuitry Controlling Local Blood Flow in the Cerebral Cortex with Optogenetics in PV::Cre Transgenic Mice.

Urban A, Rancillac A, Martinez L, Rossier J - Front Pharmacol (2012)

Bottom Line: Recent optogenetic experiments combined with functional magnetic resonance imaging have revealed that light stimulation of neurons expressing the calcium binding protein parvalbumin (PV) is associated with positive blood oxygen level-dependent (BOLD) signal in the corresponding barrel field but also with negative BOLD in the surrounding deeper area.Here, we demonstrate that in acute brain slices, channelrhodopsin-2 (ChR2) based photostimulation of PV containing neurons gives rise to an effective contraction of penetrating arterioles.These results support the neurogenic hypothesis of a complex distributed nervous system controlling the CBF.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Neurobiologie, Equipe Optogenetics and Brain Imaging, CNRS UMR 7637, Ecole Supérieure de Physique et de Chimie Industrielles ParisTech PARIS, France.

ABSTRACT
Although it is know since more than a century that neuronal activity is coupled to blood supply regulation, the underlying pathways remains to be identified. In the brain, neuronal activation triggers a local increase of cerebral blood flow (CBF) that is controlled by the neurogliovascular unit composed of terminals of neurons, astrocytes, and blood vessel muscles. It is generally accepted that the regulation of the neurogliovascular unit is adjusted to local metabolic demand by local circuits. Today experimental data led us to realize that the regulatory mechanisms are more complex and that a neuronal system within the brain is devoted to the control of local brain-blood flow. Recent optogenetic experiments combined with functional magnetic resonance imaging have revealed that light stimulation of neurons expressing the calcium binding protein parvalbumin (PV) is associated with positive blood oxygen level-dependent (BOLD) signal in the corresponding barrel field but also with negative BOLD in the surrounding deeper area. Here, we demonstrate that in acute brain slices, channelrhodopsin-2 (ChR2) based photostimulation of PV containing neurons gives rise to an effective contraction of penetrating arterioles. These results support the neurogenic hypothesis of a complex distributed nervous system controlling the CBF.

No MeSH data available.


Related in: MedlinePlus

Activation of PV interneurons by blue light. (A) Schematic diagram of a coronal brain slice used in our study. A blue circle represents the size of illuminated area. (B) Voltage-clamp recording demonstrating inward current induced by blue laser light (left). Histogram of peak steady-state photocurrent in response to light stimulation (mean 600 ± 120 pA, n = 7 FS cells in three animals, 1 s stimulus, 35 mW mm−2 output power). (C) Bright field (top panel IR-DIC) and fluorescence (bottom panel EYFP) images in the region of recorded neurons. (D) Whole-cell current-clamp recording of PV interneuron expressing ChETA-EYFP in response to patterned light stimulation at 10 or 150 Hz.
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Figure 3: Activation of PV interneurons by blue light. (A) Schematic diagram of a coronal brain slice used in our study. A blue circle represents the size of illuminated area. (B) Voltage-clamp recording demonstrating inward current induced by blue laser light (left). Histogram of peak steady-state photocurrent in response to light stimulation (mean 600 ± 120 pA, n = 7 FS cells in three animals, 1 s stimulus, 35 mW mm−2 output power). (C) Bright field (top panel IR-DIC) and fluorescence (bottom panel EYFP) images in the region of recorded neurons. (D) Whole-cell current-clamp recording of PV interneuron expressing ChETA-EYFP in response to patterned light stimulation at 10 or 150 Hz.

Mentions: Blood vessels with >50 μm of their length in focus and exhibiting a well-defined luminal diameter (8–30 μm) were selected for vascular reactivity. Images of blood vessels were acquired every 15 s using Image Pro Plus 6.1 (Media Cybernetics, San Diego, CA, USA), and baselines was determined for 5 min. Blood vessels with unstable baseline were discarded from the analyses. Optical stimulation of FS-PV interneurons was performed using the optoLED system (Cairn Research, Faversham, UK), consisting of a 470-nm, 3.5 W LED mounted on an BX51WI microscope (Olympus) equipped with infrared DIC optics (900 nm) and epifluorescence (Figure 3C). Targeted optogenetic stimulation was applied during 2 min (20 Hz, 5 ms pulse width). The illuminated spot was around 2 mm (Figure 3A) corresponding to the area of the slice visualized using a 40×/0.8 numerical aperture water-immersion objective. Luminal diameter changes were quantified off-line at different locations along the blood vessel using custom written routines running within Igor Pro software (WaveMetrics, Portland, OR, USA) to determine the spot of maximum diameter change.


Deciphering the Neuronal Circuitry Controlling Local Blood Flow in the Cerebral Cortex with Optogenetics in PV::Cre Transgenic Mice.

Urban A, Rancillac A, Martinez L, Rossier J - Front Pharmacol (2012)

Activation of PV interneurons by blue light. (A) Schematic diagram of a coronal brain slice used in our study. A blue circle represents the size of illuminated area. (B) Voltage-clamp recording demonstrating inward current induced by blue laser light (left). Histogram of peak steady-state photocurrent in response to light stimulation (mean 600 ± 120 pA, n = 7 FS cells in three animals, 1 s stimulus, 35 mW mm−2 output power). (C) Bright field (top panel IR-DIC) and fluorescence (bottom panel EYFP) images in the region of recorded neurons. (D) Whole-cell current-clamp recording of PV interneuron expressing ChETA-EYFP in response to patterned light stimulation at 10 or 150 Hz.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3375480&req=5

Figure 3: Activation of PV interneurons by blue light. (A) Schematic diagram of a coronal brain slice used in our study. A blue circle represents the size of illuminated area. (B) Voltage-clamp recording demonstrating inward current induced by blue laser light (left). Histogram of peak steady-state photocurrent in response to light stimulation (mean 600 ± 120 pA, n = 7 FS cells in three animals, 1 s stimulus, 35 mW mm−2 output power). (C) Bright field (top panel IR-DIC) and fluorescence (bottom panel EYFP) images in the region of recorded neurons. (D) Whole-cell current-clamp recording of PV interneuron expressing ChETA-EYFP in response to patterned light stimulation at 10 or 150 Hz.
Mentions: Blood vessels with >50 μm of their length in focus and exhibiting a well-defined luminal diameter (8–30 μm) were selected for vascular reactivity. Images of blood vessels were acquired every 15 s using Image Pro Plus 6.1 (Media Cybernetics, San Diego, CA, USA), and baselines was determined for 5 min. Blood vessels with unstable baseline were discarded from the analyses. Optical stimulation of FS-PV interneurons was performed using the optoLED system (Cairn Research, Faversham, UK), consisting of a 470-nm, 3.5 W LED mounted on an BX51WI microscope (Olympus) equipped with infrared DIC optics (900 nm) and epifluorescence (Figure 3C). Targeted optogenetic stimulation was applied during 2 min (20 Hz, 5 ms pulse width). The illuminated spot was around 2 mm (Figure 3A) corresponding to the area of the slice visualized using a 40×/0.8 numerical aperture water-immersion objective. Luminal diameter changes were quantified off-line at different locations along the blood vessel using custom written routines running within Igor Pro software (WaveMetrics, Portland, OR, USA) to determine the spot of maximum diameter change.

Bottom Line: Recent optogenetic experiments combined with functional magnetic resonance imaging have revealed that light stimulation of neurons expressing the calcium binding protein parvalbumin (PV) is associated with positive blood oxygen level-dependent (BOLD) signal in the corresponding barrel field but also with negative BOLD in the surrounding deeper area.Here, we demonstrate that in acute brain slices, channelrhodopsin-2 (ChR2) based photostimulation of PV containing neurons gives rise to an effective contraction of penetrating arterioles.These results support the neurogenic hypothesis of a complex distributed nervous system controlling the CBF.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Neurobiologie, Equipe Optogenetics and Brain Imaging, CNRS UMR 7637, Ecole Supérieure de Physique et de Chimie Industrielles ParisTech PARIS, France.

ABSTRACT
Although it is know since more than a century that neuronal activity is coupled to blood supply regulation, the underlying pathways remains to be identified. In the brain, neuronal activation triggers a local increase of cerebral blood flow (CBF) that is controlled by the neurogliovascular unit composed of terminals of neurons, astrocytes, and blood vessel muscles. It is generally accepted that the regulation of the neurogliovascular unit is adjusted to local metabolic demand by local circuits. Today experimental data led us to realize that the regulatory mechanisms are more complex and that a neuronal system within the brain is devoted to the control of local brain-blood flow. Recent optogenetic experiments combined with functional magnetic resonance imaging have revealed that light stimulation of neurons expressing the calcium binding protein parvalbumin (PV) is associated with positive blood oxygen level-dependent (BOLD) signal in the corresponding barrel field but also with negative BOLD in the surrounding deeper area. Here, we demonstrate that in acute brain slices, channelrhodopsin-2 (ChR2) based photostimulation of PV containing neurons gives rise to an effective contraction of penetrating arterioles. These results support the neurogenic hypothesis of a complex distributed nervous system controlling the CBF.

No MeSH data available.


Related in: MedlinePlus