Vasculo-Neuronal Coupling: Retrograde Vascular Communication to Brain Neurons.
Continuous cerebral blood flow is essential for neuronal survival, but whether vascular tone influences resting neuronal function is not known. Using a multidisciplinary approach in both rat and mice brain slices, we determined whether flow/pressure-evoked increases or decreases in parenchymal arteriole vascular tone, which result in arteriole constriction and dilation, respectively, altered resting cortical pyramidal neuron activity. We present evidence for intercellular communication in the brain involving a flow of information from vessel to astrocyte to neuron, a direction opposite to that of classic neurovascular coupling and referred to here as vasculo-neuronal coupling (VNC). Flow/pressure increases within parenchymal arterioles increased vascular tone and simultaneously decreased resting pyramidal neuron firing activity. On the other hand, flow/pressure decreases evoke parenchymal arteriole dilation and increased resting pyramidal neuron firing activity. In GLAST-CreERT2; R26-lsl-GCaMP3 mice, we demonstrate that increased parenchymal arteriole tone significantly increased intracellular calcium in perivascular astrocyte processes, the onset of astrocyte calcium changes preceded the inhibition of cortical pyramidal neuronal firing activity. During increases in parenchymal arteriole tone, the pyramidal neuron response was unaffected by blockers of nitric oxide, GABAA, glutamate, or ecto-ATPase. However, VNC was abrogated by TRPV4 channel, GABAB, as well as an adenosine A1receptor blocker. Differently to pyramidal neuron responses, increases in flow/pressure within parenchymal arterioles increased the firing activity of a subtype of interneuron. Together, these data suggest that VNC is a complex constitutive active process that enables neurons to efficiently adjust their resting activity according to brain perfusion levels, thus safeguarding cellular homeostasis by preventing mismatches between energy supply and demand.



We present evidence for vessel-to-neuron communication in the brain slice defined here as vasculo-neuronal coupling. We showed that, in response to increases in parenchymal arteriole tone, astrocyte intracellular Ca2+increased and cortical neuronal activity decreased. On the other hand, decreasing parenchymal arteriole tone increased resting cortical pyramidal neuron activity. Vasculo-neuronal coupling was partly mediated by TRPV4 channels as genetic ablation, or pharmacological blockade impaired increased flow/pressure-evoked neuronal inhibition. Increased flow/pressure-evoked neuronal inhibition was blocked in the presence of adenosine A1 receptor and GABABreceptor blockade. Results provide evidence for the concept of vasculo-neuronal coupling and highlight the importance of understanding the interplay between basal CBF and resting neuronal activity.
Department of Physiology, Augusta University, Augusta, Georgia 30912.
Ki Jung
KJ
Kim
Department of Physiology, Augusta University, Augusta, Georgia 30912.
Juan
J
Ramiro Diaz
Department of Physiology, Augusta University, Augusta, Georgia 30912.
Jennifer A
JA
Iddings
Department of Physiology, Augusta University, Augusta, Georgia 30912 jfilosa@augusta.edu.
Jessica A
JA
Filosa
D000818:Animals; D001160:Arterioles / Q000294:innervation / Q000502:physiology; D001253:Astrocytes / Q000502:physiology; D001808:Blood Vessels / Q000187:drug effects / Q000294:innervation*; D001921:Brain / Q000166:cytology / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology; D027341:Excitatory Amino Acid Transporter 1 / Q000235:genetics / Q000502:physiology; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D017966:Pyramidal Cells / Q000502:physiology; D050916:TRPV Cation Channels / Q000235:genetics / Q000502:physiology
D027341:Excitatory Amino Acid Transporter 1; C493393:Slc1a3 protein, mouse; D050916:TRPV Cation Channels; C486576:Trpv4 protein, mouse; D002118:Calcium
TRPV4 channels; adenosine; astrocytes; calcium; myogenic tone; neurovascular coupling