Armelle Rancillac | Collège de France (original) (raw)

Papers by Armelle Rancillac

We report on local superficial blood flow monitoring in biological tissue from laser Doppler holo... more We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time-averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency-shifted reference beam, permits frequency-selective imaging in the radiofrequency range. These Doppler images are acquired with an off-axis Mach-Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse-method analysis of local first-order optical fluctuation spectra at low radiofrequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1-10 mm/s range in vitro and imaging of superficial blood perfusion with a spatial resolution of about 10 micrometers in rodent models of cortical and retinal blood flow.

Sleep has been hypothesised to maintain a close relationship with metabolism. Here we focus on th... more Sleep has been hypothesised to maintain a close relationship with metabolism. Here we focus on the brain structure that triggers slow-wave sleep, the ventrolateral preoptic nucleus (VLPO), to explore the cellular and molecular signalling pathways recruited by an increase in glucose concentration. We used infrared videomicroscopy on ex vivo brain slices to establish that glucose induces vasodilations specifically in the VLPO via the astrocytic release of adenosine. Real-time detection by in situ purine biosensors further revealed that the adenosine level doubles in response to glucose, and triples during the wakefulness period. Finally, patch-clamp recordings uncovered the depolarizing effect of adenosine and its A 2A receptor agonist, CGS-21680, on sleep-promoting VLPO neurons. Altogether, our results provide new insights into the metabolically driven release of adenosine. We hypothesise that adenosine adjusts the local energy supply to local neuronal activity in response to glucose. This pathway could contribute to sleep-wake transition and sleep intensity. Sleep disorders occur worldwide and are comorbid with numerous pathologies including obesity, diabetes, heart attack, depression and stroke. Although our understanding of the physiological mechanisms of sleep induction and maintenance are far from complete, several key aspects regarding wakefulness have been resolved. Specifically, this tightly regulated state of consciousness results from a combination of drives, among which the homeostatic sleep drive is one of the strongest 1. Indeed, cerebrospinal fluid contains several sleep-promoting factors that accumulate during wakefulness including adenosine (ADO), which is considered to be the most potent. This endogenous sleep-promoting factor modulates the duration and intensity of slow-wave sleep (SWS) 2,3. Only two out of the four adenosine receptor subtypes (A 1 , A 2A , A 2B and A 3) have been shown to mediate the sleep-inducing effects of adenosine: the inhibitory G protein-coupled adenosine A 1 receptor (A 1 R) and the excit-atory G protein-coupled adenosine A 2A receptor (A 2A R) 3. In the ventrolateral preoptic nucleus (VLPO), which contains the GABAergic and galaninergic neurons responsible for SWS onset and maintenance 4–6 , ADO acting through A 1 R is proposed to indirectly promote sleep via the disinhibition of sleep-active neurons, whereas activation of A 2A R could directly stimulate these neurons 7–9. However, proof for the direct activation of sleep-promoting neurons by ADO is still debated 10,11. One energy hypothesis of sleep has posited that the function of sleep is to restore brain energy metabolism, with extracellular ADO levels allowing the brain to assess the need for sleep 12. Indeed, energy stores decrease during the metabolically active waking period and are restored during sleep 12,13. Although the function of sleep in regulating energy metabolism seems more complex than initially proposed 14,15 , wakefulness in rodents is known to be reduced after a meal and to increase during fasting 16. Moreover, glucose is reported ex vivo to directly inhibit the neuronal firing rate of orexinergic neurons that are responsible for wake promotion 17 and, conversely, to excite VLPO sleep-promoting neurons identified according to their inhibitory response to bath-applied noradrenalin (NA) 8,18–20. By monitoring the gating of their ATP-sensitive potassium channels (K ATP) these sleep-active neurons adapt their firing frequency according to the extracellular glucose concentration 21. In contrast, neighbouring neurons depolarized by NA are glucose-insensitive 21. Furthermore, bilateral microinjection in vivo of glucose into

Armelle Rancillac, 2016

Serotonin (5-HT) is a monoamine neurotransmitter that plays major roles in several physiological ... more Serotonin (5-HT) is a monoamine neurotransmitter that plays major roles in several physiological functions including circadian rhythmicity, thermoregulation, emotion, cognition and nociception. The relationship between 5-HT and sleep was demonstrated by several experiments. In a particularly elegant one, cats were rendered insomniac following the injection of a 5-HT synthesis inhibitor. In this model, the preoptic area of the hypothalamus containing the ventrolateral preoptic area (VLPO) was the only brain region in which microinjections of the 5-HT precursor could restore long periods of sleep . The VLPO being the main brain structure inducing slow-wave sleep (SWS), it was then hypothesized that 5-HT modulation of neuronal activity in this structure is essential for sleep regulation. However, the mechanisms involved in the physiological role of 5-HT within the VLPO remained largely unknown.

The characterization of neuronal properties is a necessary first step toward understanding how th... more The characterization of neuronal properties is a necessary first step toward understanding how the ventro-lateral preoptic nucleus (VLPO) neuronal network regulates slow-wave sleep (SWS). Indeed, the electrophysiological heterogeneity of VLPO neurons suggests the existence of subtypes that could differently contribute in SWS induction and maintenance. The aim of the present study was to define cell classes in the VLPO using an unsupervised clustering classification method. Electrophysiological features extracted from 289 neurons recorded in whole-cell patch-clamp allowed the identification of three main classes of VLPO neurons subdivided into five distinct subpopulations (cluster 1, 2a, 2b, 3a and 3b). The high occurrence of a low-threshold calcium spike (LTS) was one of the most distinctive features of cluster 1 and 3. Since sleep-promoting neurons are generally identified by their ability to generate an LTS and by their inhibitory response to noradrenaline (NA), 189 neurons from our dataset were also tested for this neurotransmitter. Neurons from cluster 3 were the most frequently inhibited by NA. Biocytin labeling and Neurolucida reconstructions of 112 neurons furthermore revealed a small dendritic arbor of cluster 3b neurons compared, in particular, to cluster 2b neurons. Altogether, we performed an exhaustive characterization of VLPO neuronal subtypes that is a crucial step toward a better understanding of the neuronal network within the VLPO and thereby sleep physiology. Keywords Sleep-promoting neuron Á Serotonin Á Noradrenaline Á VLPO Á Ward's clustering Á Low-threshold calcium spike (LTS)

Frontiers in Neural Circuits, 2012

GABAergic interneurons are local integrators of cortical activity that have been reported to be i... more GABAergic interneurons are local integrators of cortical activity that have been reported to be involved in the control of cerebral blood flow (CBF) through their ability to produce vasoactive molecules and their rich innervation of neighboring blood vessels. They form a highly diverse population among which the serotonin 5-hydroxytryptamine 3A receptor (5-HT 3A )-expressing interneurons share a common developmental origin, in addition to the responsiveness to serotonergic ascending pathway. We have recently shown that these neurons regroup two distinct subpopulations within the somatosensory cortex: Neuropeptide Y (NPY)-expressing interneurons, displaying morphological properties similar to those of neurogliaform cells and Vasoactive Intestinal Peptide (VIP)-expressing bipolar/bitufted interneurons. The aim of the present study was to determine the role of these neuronal populations in the control of vascular tone by monitoring blood vessels diameter changes, using infrared videomicroscopy in mouse neocortical slices. Bath applications of 1-(3-Chlorophenyl)biguanide hydrochloride (mCPBG), a 5-HT 3 R agonist, induced both constrictions (30%) and dilations (70%) of penetrating arterioles within supragranular layers. All vasoconstrictions were abolished in the presence of the NPY receptor antagonist (BIBP 3226), suggesting that they were elicited by NPY release. Vasodilations persisted in the presence of the VIP receptor antagonist VPAC1 (PG-97-269), whereas they were blocked in the presence of the neuronal Nitric Oxide (NO) Synthase (nNOS) inhibitor, L-NNA. Altogether, these results strongly suggest that activation of neocortical 5-HT 3A -expressing interneurons by serotoninergic input could induces NO mediated vasodilatations and NPY mediated vasoconstrictions.

The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 8, 2015

Sleep-active neurons located in the ventrolateral preoptic nucleus (VLPO) play a crucial role in ... more Sleep-active neurons located in the ventrolateral preoptic nucleus (VLPO) play a crucial role in the induction and maintenance of slow-wave sleep (SWS). However, the cellular and molecular mechanisms responsible for their activation at sleep onset remain poorly understood. Here, we test the hypothesis that a rise in extracellular glucose concentration in the VLPO can promote sleep by increasing the activity of sleep-promoting VLPO neurons. We find that infusion of a glucose concentration into the VLPO of mice promotes SWS and increases the density of c-Fos-labeled neurons selectively in the VLPO. Moreover, we show in patch-clamp recordings from brain slices that VLPO neurons exhibiting properties of sleep-promoting neurons are selectively excited by glucose within physiological range. This glucose-induced excitation implies the catabolism of glucose, leading to a closure of ATP-sensitive potassium (KATP) channels. The extracellular glucose concentration monitors the gating of KATP c...

Journal of the Optical Society of America. A, Optics, image science, and vision, 2014

We report on local superficial blood flow monitoring in biological tissue from laser Doppler holo... more We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time-averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency-shifted reference beam, permits frequency-selective imaging in the radio frequency range. These Doppler images are acquired with an off-axis Mach-Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse-method analysis of local first-order optical fluctuation spectra at low radio frequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1-10 mm/s range i...

Biomedical Optics and 3-D Imaging, 2010

ABSTRACT We report new results in angiographic mapping of microvessels in vivo with a wide field ... more ABSTRACT We report new results in angiographic mapping of microvessels in vivo with a wide field optical detection scheme, enabling blood flow contrast measurements in minimally invasive conditions without exogenous marker.

Journal of Neuroscience, 2004

The role of interneurons in neurovascular coupling was investigated by patch-clamp recordings in ... more The role of interneurons in neurovascular coupling was investigated by patch-clamp recordings in acute rat cortical slices, followed by single-cell reverse transcriptase-multiplex PCR (RT-mPCR) and confocal observation of biocytin-filled neurons, laminin-stained microvessels, and immunodetection of their afferents by vasoactive subcortical cholinergic (ACh) and serotonergic (5-HT) pathways. The evoked firing of single interneurons in whole-cell recordings was sufficient to either dilate or constrict neighboring microvessels.

Journal of Neuroscience, 2006

The tight coupling between increased neuronal activity and local cerebral blood flow, known as fu... more The tight coupling between increased neuronal activity and local cerebral blood flow, known as functional hyperemia, is essential for normal brain function. However, its cellular and molecular mechanisms remain poorly understood. In the cerebellum, functional hyperemia depends almost exclusively on nitric oxide (NO). Here, we investigated the role of different neuronal populations in the control of microvascular tone by in situ amperometric detection of NO and infrared videomicroscopy of microvessel movements in rat cerebellar

Optics Letters, 2006

We present a new instrument, based on a low frame rate (8 Hz) CCD camera used in a heterodyne opt... more We present a new instrument, based on a low frame rate (8 Hz) CCD camera used in a heterodyne optical-mixing configuration, that can create wide-field laser Doppler maps. As an illustration, we show results obtained in a mouse brain, in vivo, showing the Doppler signature of blood flow. The instrument is based on the frequency-shifting digital holography scheme.

Journal of Neuroscience Research, 2009

Table 2: Morphological somatodendritic properties of transgenic and wild type NPY-interneurons Su... more Table 2: Morphological somatodendritic properties of transgenic and wild type NPY-interneurons Supplementary

Journal of Biomedical Optics, 2007

We report the assessment of cerebral blood flow (CBF) changes with a wide-field laser Doppler ima... more We report the assessment of cerebral blood flow (CBF) changes with a wide-field laser Doppler imager based on a CCD camera detection scheme, in vivo, in mice. The setup enables the acquisition of data in minimally invasive conditions. In contrast with conventional laser Doppler velocimeters and imagers, the Doppler signature of moving scatterers is measured in the frequency domain, by detuning a heterodyne optical detection. The quadratic mean of the measured frequency shift is used as an indicator of CBF. We observe a significant variability of this indicator in an experiment designed to induce blood flow changes.

Frontiers in Pharmacology, 2012

Although it is know since more than a century that neuronal activity is coupled to blood supply r... more 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.

We report on local superficial blood flow monitoring in biological tissue from laser Doppler holo... more We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time-averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency-shifted reference beam, permits frequency-selective imaging in the radiofrequency range. These Doppler images are acquired with an off-axis Mach-Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse-method analysis of local first-order optical fluctuation spectra at low radiofrequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1-10 mm/s range in vitro and imaging of superficial blood perfusion with a spatial resolution of about 10 micrometers in rodent models of cortical and retinal blood flow.

Sleep has been hypothesised to maintain a close relationship with metabolism. Here we focus on th... more Sleep has been hypothesised to maintain a close relationship with metabolism. Here we focus on the brain structure that triggers slow-wave sleep, the ventrolateral preoptic nucleus (VLPO), to explore the cellular and molecular signalling pathways recruited by an increase in glucose concentration. We used infrared videomicroscopy on ex vivo brain slices to establish that glucose induces vasodilations specifically in the VLPO via the astrocytic release of adenosine. Real-time detection by in situ purine biosensors further revealed that the adenosine level doubles in response to glucose, and triples during the wakefulness period. Finally, patch-clamp recordings uncovered the depolarizing effect of adenosine and its A 2A receptor agonist, CGS-21680, on sleep-promoting VLPO neurons. Altogether, our results provide new insights into the metabolically driven release of adenosine. We hypothesise that adenosine adjusts the local energy supply to local neuronal activity in response to glucose. This pathway could contribute to sleep-wake transition and sleep intensity. Sleep disorders occur worldwide and are comorbid with numerous pathologies including obesity, diabetes, heart attack, depression and stroke. Although our understanding of the physiological mechanisms of sleep induction and maintenance are far from complete, several key aspects regarding wakefulness have been resolved. Specifically, this tightly regulated state of consciousness results from a combination of drives, among which the homeostatic sleep drive is one of the strongest 1. Indeed, cerebrospinal fluid contains several sleep-promoting factors that accumulate during wakefulness including adenosine (ADO), which is considered to be the most potent. This endogenous sleep-promoting factor modulates the duration and intensity of slow-wave sleep (SWS) 2,3. Only two out of the four adenosine receptor subtypes (A 1 , A 2A , A 2B and A 3) have been shown to mediate the sleep-inducing effects of adenosine: the inhibitory G protein-coupled adenosine A 1 receptor (A 1 R) and the excit-atory G protein-coupled adenosine A 2A receptor (A 2A R) 3. In the ventrolateral preoptic nucleus (VLPO), which contains the GABAergic and galaninergic neurons responsible for SWS onset and maintenance 4–6 , ADO acting through A 1 R is proposed to indirectly promote sleep via the disinhibition of sleep-active neurons, whereas activation of A 2A R could directly stimulate these neurons 7–9. However, proof for the direct activation of sleep-promoting neurons by ADO is still debated 10,11. One energy hypothesis of sleep has posited that the function of sleep is to restore brain energy metabolism, with extracellular ADO levels allowing the brain to assess the need for sleep 12. Indeed, energy stores decrease during the metabolically active waking period and are restored during sleep 12,13. Although the function of sleep in regulating energy metabolism seems more complex than initially proposed 14,15 , wakefulness in rodents is known to be reduced after a meal and to increase during fasting 16. Moreover, glucose is reported ex vivo to directly inhibit the neuronal firing rate of orexinergic neurons that are responsible for wake promotion 17 and, conversely, to excite VLPO sleep-promoting neurons identified according to their inhibitory response to bath-applied noradrenalin (NA) 8,18–20. By monitoring the gating of their ATP-sensitive potassium channels (K ATP) these sleep-active neurons adapt their firing frequency according to the extracellular glucose concentration 21. In contrast, neighbouring neurons depolarized by NA are glucose-insensitive 21. Furthermore, bilateral microinjection in vivo of glucose into

Armelle Rancillac, 2016

Serotonin (5-HT) is a monoamine neurotransmitter that plays major roles in several physiological ... more Serotonin (5-HT) is a monoamine neurotransmitter that plays major roles in several physiological functions including circadian rhythmicity, thermoregulation, emotion, cognition and nociception. The relationship between 5-HT and sleep was demonstrated by several experiments. In a particularly elegant one, cats were rendered insomniac following the injection of a 5-HT synthesis inhibitor. In this model, the preoptic area of the hypothalamus containing the ventrolateral preoptic area (VLPO) was the only brain region in which microinjections of the 5-HT precursor could restore long periods of sleep . The VLPO being the main brain structure inducing slow-wave sleep (SWS), it was then hypothesized that 5-HT modulation of neuronal activity in this structure is essential for sleep regulation. However, the mechanisms involved in the physiological role of 5-HT within the VLPO remained largely unknown.

The characterization of neuronal properties is a necessary first step toward understanding how th... more The characterization of neuronal properties is a necessary first step toward understanding how the ventro-lateral preoptic nucleus (VLPO) neuronal network regulates slow-wave sleep (SWS). Indeed, the electrophysiological heterogeneity of VLPO neurons suggests the existence of subtypes that could differently contribute in SWS induction and maintenance. The aim of the present study was to define cell classes in the VLPO using an unsupervised clustering classification method. Electrophysiological features extracted from 289 neurons recorded in whole-cell patch-clamp allowed the identification of three main classes of VLPO neurons subdivided into five distinct subpopulations (cluster 1, 2a, 2b, 3a and 3b). The high occurrence of a low-threshold calcium spike (LTS) was one of the most distinctive features of cluster 1 and 3. Since sleep-promoting neurons are generally identified by their ability to generate an LTS and by their inhibitory response to noradrenaline (NA), 189 neurons from our dataset were also tested for this neurotransmitter. Neurons from cluster 3 were the most frequently inhibited by NA. Biocytin labeling and Neurolucida reconstructions of 112 neurons furthermore revealed a small dendritic arbor of cluster 3b neurons compared, in particular, to cluster 2b neurons. Altogether, we performed an exhaustive characterization of VLPO neuronal subtypes that is a crucial step toward a better understanding of the neuronal network within the VLPO and thereby sleep physiology. Keywords Sleep-promoting neuron Á Serotonin Á Noradrenaline Á VLPO Á Ward's clustering Á Low-threshold calcium spike (LTS)

Frontiers in Neural Circuits, 2012

GABAergic interneurons are local integrators of cortical activity that have been reported to be i... more GABAergic interneurons are local integrators of cortical activity that have been reported to be involved in the control of cerebral blood flow (CBF) through their ability to produce vasoactive molecules and their rich innervation of neighboring blood vessels. They form a highly diverse population among which the serotonin 5-hydroxytryptamine 3A receptor (5-HT 3A )-expressing interneurons share a common developmental origin, in addition to the responsiveness to serotonergic ascending pathway. We have recently shown that these neurons regroup two distinct subpopulations within the somatosensory cortex: Neuropeptide Y (NPY)-expressing interneurons, displaying morphological properties similar to those of neurogliaform cells and Vasoactive Intestinal Peptide (VIP)-expressing bipolar/bitufted interneurons. The aim of the present study was to determine the role of these neuronal populations in the control of vascular tone by monitoring blood vessels diameter changes, using infrared videomicroscopy in mouse neocortical slices. Bath applications of 1-(3-Chlorophenyl)biguanide hydrochloride (mCPBG), a 5-HT 3 R agonist, induced both constrictions (30%) and dilations (70%) of penetrating arterioles within supragranular layers. All vasoconstrictions were abolished in the presence of the NPY receptor antagonist (BIBP 3226), suggesting that they were elicited by NPY release. Vasodilations persisted in the presence of the VIP receptor antagonist VPAC1 (PG-97-269), whereas they were blocked in the presence of the neuronal Nitric Oxide (NO) Synthase (nNOS) inhibitor, L-NNA. Altogether, these results strongly suggest that activation of neocortical 5-HT 3A -expressing interneurons by serotoninergic input could induces NO mediated vasodilatations and NPY mediated vasoconstrictions.

The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 8, 2015

Sleep-active neurons located in the ventrolateral preoptic nucleus (VLPO) play a crucial role in ... more Sleep-active neurons located in the ventrolateral preoptic nucleus (VLPO) play a crucial role in the induction and maintenance of slow-wave sleep (SWS). However, the cellular and molecular mechanisms responsible for their activation at sleep onset remain poorly understood. Here, we test the hypothesis that a rise in extracellular glucose concentration in the VLPO can promote sleep by increasing the activity of sleep-promoting VLPO neurons. We find that infusion of a glucose concentration into the VLPO of mice promotes SWS and increases the density of c-Fos-labeled neurons selectively in the VLPO. Moreover, we show in patch-clamp recordings from brain slices that VLPO neurons exhibiting properties of sleep-promoting neurons are selectively excited by glucose within physiological range. This glucose-induced excitation implies the catabolism of glucose, leading to a closure of ATP-sensitive potassium (KATP) channels. The extracellular glucose concentration monitors the gating of KATP c...

Journal of the Optical Society of America. A, Optics, image science, and vision, 2014

We report on local superficial blood flow monitoring in biological tissue from laser Doppler holo... more We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time-averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency-shifted reference beam, permits frequency-selective imaging in the radio frequency range. These Doppler images are acquired with an off-axis Mach-Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse-method analysis of local first-order optical fluctuation spectra at low radio frequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1-10 mm/s range i...

Biomedical Optics and 3-D Imaging, 2010

ABSTRACT We report new results in angiographic mapping of microvessels in vivo with a wide field ... more ABSTRACT We report new results in angiographic mapping of microvessels in vivo with a wide field optical detection scheme, enabling blood flow contrast measurements in minimally invasive conditions without exogenous marker.

Journal of Neuroscience, 2004

The role of interneurons in neurovascular coupling was investigated by patch-clamp recordings in ... more The role of interneurons in neurovascular coupling was investigated by patch-clamp recordings in acute rat cortical slices, followed by single-cell reverse transcriptase-multiplex PCR (RT-mPCR) and confocal observation of biocytin-filled neurons, laminin-stained microvessels, and immunodetection of their afferents by vasoactive subcortical cholinergic (ACh) and serotonergic (5-HT) pathways. The evoked firing of single interneurons in whole-cell recordings was sufficient to either dilate or constrict neighboring microvessels.

Journal of Neuroscience, 2006

The tight coupling between increased neuronal activity and local cerebral blood flow, known as fu... more The tight coupling between increased neuronal activity and local cerebral blood flow, known as functional hyperemia, is essential for normal brain function. However, its cellular and molecular mechanisms remain poorly understood. In the cerebellum, functional hyperemia depends almost exclusively on nitric oxide (NO). Here, we investigated the role of different neuronal populations in the control of microvascular tone by in situ amperometric detection of NO and infrared videomicroscopy of microvessel movements in rat cerebellar

Optics Letters, 2006

We present a new instrument, based on a low frame rate (8 Hz) CCD camera used in a heterodyne opt... more We present a new instrument, based on a low frame rate (8 Hz) CCD camera used in a heterodyne optical-mixing configuration, that can create wide-field laser Doppler maps. As an illustration, we show results obtained in a mouse brain, in vivo, showing the Doppler signature of blood flow. The instrument is based on the frequency-shifting digital holography scheme.

Journal of Neuroscience Research, 2009

Table 2: Morphological somatodendritic properties of transgenic and wild type NPY-interneurons Su... more Table 2: Morphological somatodendritic properties of transgenic and wild type NPY-interneurons Supplementary

Journal of Biomedical Optics, 2007

We report the assessment of cerebral blood flow (CBF) changes with a wide-field laser Doppler ima... more We report the assessment of cerebral blood flow (CBF) changes with a wide-field laser Doppler imager based on a CCD camera detection scheme, in vivo, in mice. The setup enables the acquisition of data in minimally invasive conditions. In contrast with conventional laser Doppler velocimeters and imagers, the Doppler signature of moving scatterers is measured in the frequency domain, by detuning a heterodyne optical detection. The quadratic mean of the measured frequency shift is used as an indicator of CBF. We observe a significant variability of this indicator in an experiment designed to induce blood flow changes.

Frontiers in Pharmacology, 2012

Although it is know since more than a century that neuronal activity is coupled to blood supply r... more 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.