1st Speaker: Katsuya Ozawa (Hirase Lab)

"Cerebral Blood Flow Modulation by Basal Forebrain or Whisker Stimulation Can Occur Independently of Large Cytosolic Ca2+ Signaling in Astrocytes"

Katsuya Ozawa (Neuron-Glia Circuitry Team)

Activation of the nucleus basalis of Meynert (NBM), the primary source of cholinergic projection to the cerebral cortex, has been reported to cause significant changes in cerebral cortical blood flow (CBF) in rodents. The NBM-driven increase of CBF has been described to be dependent in part on muscarinic acetylcholine receptors (mAChRs). Lately, several groups reported that astrocytes modulate local CBF via intracellular Ca2+ signaling. Considering that cortical astrocytes express mAChRs and in vivo activation of NBM leads to mAChR-dependent Ca2+ surges in astrocytes, cholinergic modulation of CBF via astrocytic Ca2+ surges is conceivable. We report here that a brief stimulation of the NBM induces a biphasic CBF response as measured by laser Doppler flowmetry in the somatosensory cortex of C57BL/6J mice. This response consists of a rapid increase, followed by an overshooting slower decrease that goes back to baseline within a minute. The stNBM-induced CBF response was sensitive to the mAChR antagonist atropine. Surprisingly, we find that IP3R2 knockout mice, which lack cytosolic Ca2+ surges in astrocytes, show a similar CBF response to stNBM. Moreover, whisker stimulation resulted in similar degrees of CBF increase in IP3R2 knockout mice and the background strain C57BL/6J. Our results show that neural activity-driven CBF modulation can occur without large cytosolic Ca2+ increases in astrocytes.

2002 – 2009 Technical staff, Laboratory for Visual Neurocomputing, RIKEN BSI
2009 – 2010 Technical staff, Laboratory for Structural Physiology, University of Tokyo
2010 – 2012 Technical staff, RIKEN BSI-TOYOTA Collaboration Center, RIKEN BSI
2012 – present Technical staff, Laboratory for Neuron-Glia Circuitry, RIKEN BSI