Vasoactive signaling from astrocytes is an important contributor to the neurovascular coupling (NVC), which aims at providing energy to neurons during brain activation by increasing blood perfusion in the surrounding vasculature. Pharmacological manipulations have been previously combined with experimental techniques (e.g., transgenic mice, uncaging, and multiphoton microscopy) and stimulation paradigms to isolate in vivo individual pathways of the astrocyte-mediated NVC. Unfortunately, these pathways are highly nonlinear and non-additive. To separate these pathways in a unified framework, we combine a comprehensive biophysical model of vasoactive signaling from astrocytes with a unique optogenetic stimulation method that selectively induces astrocytic Ca2+ signaling in a large population of astrocytes. We also use a sensitivity analysis and an optimization technique to estimate key model parameters. Optogenetically-induced Ca2+ signals in astrocytes cause a cerebral blood flow (CBF) response with two major components. Component-1 was rapid and smaller (ΔCBF∼13%, 18 seconds), while component-2 was slowest and highest (ΔCBF ∼18%, 45 seconds). The proposed biophysical model was adequate in reproducing component-2, which was validated with a pharmacological manipulation. Model’s predictions were not in contradiction with previous studies. Finally, we discussed scenarios accounting for the existence of component-1, which once validated might be included in our model.
HeegerDJRessD.What does fMRI tell us about neuronal activity?Nat Rev Neurosci2002;
3: 142–151.
2.
HarderDRAlkayedNJLangeAR, et al.
Functional hyperemia in the brain: hypothesis for astrocyte-derived vasodilator metabolites. Stroke1998;
29: 229–234.
3.
AttwellDBuchanAMCharpakS, et al.
Glial and neuronal control of brain blood flow. Nature2010;
468: 232–243.
4.
RieraJJSumiyoshiA.Brain oscillations: ideal scenery to understand the neurovascular coupling. Curr Opin Neurol2010;
23: 374–381.
5.
HalassaMMFellinTTakanoH, et al.
Synaptic islands defined by the territory of a single astrocyte. J Neurosci2007;
27: 6473–6477.
6.
BlutsteinTHaydonPG. Chapter five – the tripartite synapse: a role for glial cells in modulating synaptic transmission. In: The synapse. 1st ed. New York: Academic Press, 2014. pp. 155–172.
7.
LecruxCHamelE.The neurovascular unit in brain function and disease. Acta Physiol (Oxf)2011;
203: 47–59.
8.
SchaefferSIadecolaC.Revisiting the neurovascular unit. Nat Neurosci2021;
24: 1198–1209.
9.
AlkayedNJBirksEKNarayananJ, et al.
Role of P-450 arachidonic acid epoxygenase in the response of cerebral blood flow to glutamate in rats. Stroke1997;
28: 1066–1072.
10.
PengXZhangCAlkayedNJ, et al.
Dependency of cortical functional hyperemia to forepaw stimulation on epoxygenase and nitric oxide synthase activities in rats. J Cereb Blood Flow Metab2004;
24: 509–517.
11.
PickardJD.Role of prostaglandins and arachidonic acid derivatives in the coupling of cerebral blood flow to cerebral metabolism. J Cereb Blood Flow Metab1981;
1: 361–384.
12.
PriceDLLudwigJWMiH, et al.
Distribution of rSlo Ca2+-activated K+ channels in rat astrocyte perivascular endfeet. Brain Res2002;
956: 183–193.
13.
FilosaJABonevADStraubSV, et al.
Local potassium signaling couples neuronal activity to vasodilation in the brain. Nat Neurosci2006;
9: 1397–1403.
14.
WangXLouNXuQ, et al.
Astrocytic Ca2+ signaling evoked by sensory stimulation in vivo. Nat Neurosci2006;
9: 816–823.
15.
LindBLBrazheARJessenSB, et al.
Rapid stimulus-evoked astrocyte Ca2+ elevations and hemodynamic responses in mouse somatosensory cortex in vivo. Proc Natl Acad Sci U S A2013;
110: E4678–E4687.
16.
LindBLJessenSBLønstrupM, et al.
Fast Ca2+ responses in astrocyte end‐feet and neurovascular coupling in mice. Glia2018;
66: 348–358.
17.
LecruxCToussayXKocharyanA, et al.
Pyramidal neurons are “neurogenic hubs” in the neurovascular coupling response to whisker stimulation. J Neurosci2011;
31: 9836–9847.
18.
InstitorisAVandalMPeringodG, et al.
Astrocytes amplify neurovascular coupling to sustained activation of neocortex in awake mice. Nat Commun2022;
13: 7872.
19.
BakalovaRMatsuuraTKannoI.The cyclooxygenase inhibitors indomethacin and rofecoxib reduce regional cerebral blood flow evoked by somatosensory stimulation in rats. Exp Biol Med (Maywood)2002;
227: 465–473.
20.
TakanoTTianGFPengW, et al.
Astrocyte-mediated control of cerebral blood flow. Nat Neurosci2006;
9: 260–267.
21.
NiwaKHaenselCRossME, et al.
Cyclooxygenase-1 participates in selected vasodilator responses of the cerebral circulation. Circ Res2001;
88: 600–608.
22.
NiwaKArakiEMorhamSG, et al.
Cyclooxygenase-2 contributes to functional hyperemia in Whisker-Barrel cortex. J Neurosci2000;
20: 763–770.
23.
LacroixAToussayXAnenbergE, et al.
COX-2-derived prostaglandin E2 produced by pyramidal neurons contributes to neurovascular coupling in the rodent cerebral cortex. J Neurosci2015;
35: 11791–11810.
24.
GirouardHBonevADHannahRM, et al.
Astrocytic endfoot Ca2+ and BK channels determine both arteriolar dilation and constriction. Proc Natl Acad Sci U S A2010;
107: 3811–3816.
25.
StefanovicBSchwindtWHoehnM, et al.
Functional uncoupling of hemodynamic from neuronal response by inhibition of neuronal nitric oxide synthase. J Cereb Blood Flow Metab2007;
27: 741–754.
26.
WangHHitronIMIadecolaC, et al.
Synaptic and vascular associations of neurons containing cyclooxygenase-2 and nitric oxide synthase in rat somatosensory cortex. Cereb Cortex2005;
15: 1250–1260.
27.
MasamotoKUnekawaMWatanabeT, et al.
Unveiling astrocytic control of cerebral blood flow with optogenetics. Sci Rep2015;
5: 11455.
28.
TanakaKFMatsuiKSasakiT, et al.
Expanding the repertoire of optogenetically targeted cells with an enhanced gene expression system. Cell Rep2012;
2: 397–406.
29.
GuXChenWVolkowND, et al.
Synchronized astrocytic Ca2+ responses in neurovascular coupling during somatosensory stimulation and for the resting state. Cell Rep2018;
23: 3878–3890.
30.
KeilholzSDSilvaACRamanM, et al.
Functional MRI of the rodent somatosensory pathway using multislice echo planar imaging. Magn Reson Med2004;
52: 89–99.
31.
NishimuraMSawatariHTakemotoM, et al.
Identification of the somatosensory parietal ventral area and overlap of the somatosensory and auditory cortices in mice. Neurosci Res2015;
99: 55–61.
32.
RanczEAMoyaJDrawitschF, et al.
Widespread vestibular activation of the rodent cortex. J Neurosci2015;
35: 5926–5934.
33.
ShimHJJungWBSchlegelF, et al.
Mouse fMRI under ketamine and xylazine anesthesia: robust contralateral somatosensory cortex activation in response to forepaw stimulation. NeuroImage2018;
177: 30–44.
34.
KoehlerRCRomanRJHarderDR.Astrocytes and the regulation of cerebral blood flow. Trends Neurosci2009;
32: 160–169.
35.
YangJClarkJWBryanRM, et al.
Mathematical modeling of the nitric oxide/cGMP pathway in the vascular smooth muscle cell. Am J Physiol Heart Circ Physiol2005;
289: H886–897.
36.
KoenigsbergerMSauserRSeppeyD, et al.
Calcium dynamics and vasomotion in arteries subject to isometric, isobaric, and isotonic conditions. Biophys J2008;
95: 2728–2738.
37.
WitthoftAEm KarniadakisG.A bidirectional model for communication in the neurovascular unit. J Theor Biol2012;
311: 80–93.
38.
YamazakiYKamiyamaY.Mathematical model of wall shear stress-dependent vasomotor response based on physiological mechanisms. Comput Biol Med2014;
45: 126–135.
39.
TeslerFLinneMLDestexheA.Modeling the relationship between neuronal activity and the BOLD signal: contributions from astrocyte calcium dynamics. Sci Rep2023;
13: 6451–17.
40.
Percie Du SertNHurstVAhluwaliaA, et al.
The ARRIVE guidelines 2.0: updated guidelines for reporting animal research. J Cereb Blood Flow Metab2020;
40: 1769–1777.
41.
YouTImGHKimSG.Characterization of brain-wide somatosensory BOLD fMRI in mice under dexmedetomidine/isoflurane and ketamine/xylazine. Sci Rep2021;
11: 13110.
42.
BalachandarLMontejoKACastanoE, et al.
Simultaneous Ca2+ imaging and optogenetic stimulation of cortical astrocytes in adult murine brain slices. Curr Protoc Neurosci2020;
94: e110.
43.
MulliganSJMacVicarBA.Calcium transients in astrocyte endfeet cause cerebrovascular constrictions. Nature2004;
431: 195–199.
44.
De LucaDMinucciAPiastraM, et al.
Ex vivo effect of varespladib on secretory phospholipase A2 alveolar activity in infants with ARDS. PLoS ONE2012;
7: e47066.
45.
van VeluwSJHouSSCalvo-RodriguezM, et al.
Vasomotion as a driving force for paravascular clearance in the awake mouse brain. Neuron2020;
105: 549–561.e5.
46.
MoshkforoushABalachandarLMoncionC, et al.
Unraveling ChR2-driven stochastic Ca2+ dynamics in astrocytes: a call for new interventional paradigms. PLOS Comput Biol2021;
17: e1008648.
47.
CampbellWBFlemingI.Epoxyeicosatrienoic acids and endothelium-dependent responses. Pflugers Arch2010;
459: 881–895.
48.
SnitkoYKoduriRSHanSK, et al.
Mapping the interfacial binding surface of human secretory group IIa phospholipase A2. Biochemistry1997;
36: 14325–14333.
49.
SingerAGGhomashchiFLe CalvezC, et al.
Interfacial kinetic and binding properties of the complete set of human and mouse groups I, II, V, X, and XII secreted phospholipases A2. J Biol Chem2002;
277: 48535–48549.
50.
KimRRChenZMannTJ, et al.
Structural and functional aspects of targeting the secreted human group IIA phospholipase A2. Molecules2020;
25: 4459.
51.
LiuXLiCFalckJR, et al.
Interaction of nitric oxide, 20-HETE, and EETs during functional hyperemia in whisker barrel cortex. Am J Physiol Heart Circ Physiol2008;
295: H619–631.
52.
SuarezAValdes-HernandezPAMoshkforoushA, et al.
Arterial blood stealing as a mechanism of negative BOLD response: from the steady-flow with nonlinear phase separation to a windkessel-based model. J Theor Biol2021;
529: 110856.
53.
TothPCsiszarATucsekZ, et al.
Role of 20-HETE, TRPC channels, and BKCa in dysregulation of pressure-induced Ca2+ signaling and myogenic constriction of cerebral arteries in aged hypertensive mice. American Journal of Physiology – Heart and Circulatory Physiology2013;
305: 1698–1708.
54.
KoEAHanJJungID, et al.
Physiological roles of K+ channels in vascular smooth muscle cells. J Smooth Muscle Res2008;
44: 65–81.
55.
SteinM.Large sample properties of simulations using Latin hypercube sampling. Technometrics1987;
29: 143–151.
56.
OpländerCDeckAVolkmarCM, et al.
Mechanism and biological relevance of blue-light (420-453 nm)-induced nonenzymatic nitric oxide generation from photolabile nitric oxide derivates in human skin in vitro and in vivo. Free Radic Biol Med2013;
65: 1363–1377. Original Contribution
57.
SikkaGHussmannGPPandeyD, et al.
Melanopsin mediates light-dependent relaxation in blood vessels. Proc Natl Acad Sci U S A2014;
111: 17977–17982.
58.
RungtaRLOsmanskiBFBoidoD, et al.
Light controls cerebral blood flow in naive animals. Nat Commun2017;
8: 14191.
59.
VerkhratskyANedergaardM.Physiology of astroglia. Physiol Rev2018;
98: 239–389.
60.
KellerDEröCMarkramH.Cell densities in the mouse brain: a systematic review. Front Neuroanat2018;
12: 83. 394837.
61.
KrawchukMBRuffCFYangX, et al.
Optogenetic assessment of VIP, PV, SOM and NOS inhibitory neuron activity and cerebral blood flow regulation in mouse somato-sensory cortex. J Cereb Blood Flow Metab2020;
40: 1427–1440.
62.
EstradaCDeFelipeJ.Nitric oxide-producing neurons in the neocortex: morphological and functional relationship with intraparenchymal microvasculature. Cereb Cortex1998;
8: 193–203.
63.
WienckenAECasagrandeVA.Endothelial nitric oxide synthetase (eNOS) in astrocytes: another source of nitric oxide in neocortex. Glia1999;
26: 280–290.
64.
LongdenTADabertrandFKoideM, et al.
Capillary K+-sensing initiates retrograde hyperpolarization to increase local cerebral blood flow. Nat Neurosci2017;
20: 717–726.
65.
MoshkforoushAAshenagarBHarrazOF, et al.
The capillary kir channel as sensor and amplifier of neuronal signals: modeling insights on K+-mediated neurovascular communication. Proc Natl Acad Sci U S A2020;
117: 16626–16637.
66.
GonzalesALKlugNRMoshkforoushA, et al.
Contractile pericytes determine the direction of blood flow at capillary junctions. Proc Natl Acad Sci U S A2020;
117: 27022–27033.
67.
HartmannDACoelho-SantosVShihAY.Pericyte control of blood flow across microvascular zones in the central nervous system. Annu Rev Physiol2022;
84: 331–354.
68.
LiuTSunLXiongY, et al.
Calcium triggers exocytosis from two types of organelles in a single astrocyte. J Neurosci2011;
31: 10593–10601.
69.
LaloUPalyginOVerkhratskyA, et al.
ATP from synaptic terminals and astrocytes regulates NMDA receptors and synaptic plasticity through PSD-95 multi-protein complex. Sci Rep2016;
6: 33609–33620.
70.
GrossERNithipatikomKHsuAK, et al.
Cytochrome P450 ω-hydroxylase inhibition reduces infarct size during reperfusion via the sarcolemmal KATP channel. J Mol Cell Cardiol2004;
37: 1245–1249.
71.
HatakeyamaNUnekawaMMurataJ, et al.
Differential pial and penetrating arterial responses examined by optogenetic activation of astrocytes and neurons. J Cereb Blood Flow Metab2021;
41: 2676–2689.
72.
ZhouYXiaXMLingleCJ.The functionally relevant site for paxilline inhibition of BK channels. Proc Natl Acad Sci U S A2020;
117: 1021–1026.
73.
BilmenJGWoottonLLMichelangeliF.The mechanism of inhibition of the sarco/endoplasmic reticulum Ca2+ ATPase by paxilline. Arch Biochem Biophys2002;
406: 55–64.
BocchiLEvangelistiABarrellaM, et al.
Recovery of 0.1 Hz microvascular skin blood flow in dysautonomic diabetic (type 2) neuropathy by using frequency rhythmic electrical modulation system (FREMS). Med Eng Phys2010;
32: 407–413.
76.
SasakiDImaiKIkomaY, et al.
Plastic vasomotion entrainment. Elife2024;
13: RP93721.
77.
DrewPJMateoCTurnerKL, et al.
Ultra-slow oscillations in fMRI and resting-state connectivity: neuronal and vascular contributions and technical confounds. Neuron2020;
107: 782–804.
HaideyJNPeringodGInstitorisA, et al.
Astrocytes regulate ultra-slow arteriole oscillations via stretch-mediated TRPV4-COX-1 feedback. Cell Rep2021;
36: 109405.
80.
RieraJJWanXJimenezJC, et al.
Nonlinear local electrovascular coupling. I: a theoretical model. Hum Brain Mapp2006;
27: 896–914.
81.
SuarezAValdés-HernándezPABernalB, et al.
Identification of negative BOLD responses in epilepsy using windkessel models. Front Neurol2021;
12: 659081.
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