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Penetrating arterioles are a bottleneck in the perfusion of neocortex. Proc Natl Acad Sci U S A

Department of Physics, University of California at San Diego, La Jolla, CA 92093, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 02/2007; 104(1):365-70. DOI: 10.1073/pnas.0609551104
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ABSTRACT Penetrating arterioles bridge the mesh of communicating arterioles on the surface of cortex with the subsurface microvascular bed that feeds the underlying neural tissue. We tested the conjecture that penetrating arterioles, which are positioned to regulate the delivery of blood, are loci of severe ischemia in the event of occlusion. Focal photothrombosis was used to occlude single penetrating arterioles in rat parietal cortex, and the resultant changes in flow of red blood cells were measured with two-photon laser-scanning microscopy in individual subsurface microvessels that surround the occlusion. We observed that the average flow of red blood cells nearly stalls adjacent to the occlusion and remains within 30% of its baseline value in vessels as far as 10 branch points downstream from the occlusion. Preservation of average flow emerges 350 mum away; this length scale is consistent with the spatial distribution of penetrating arterioles. We conclude that penetrating arterioles are a bottleneck in the supply of blood to neocortex, at least to superficial layers.

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Available from: Nozomi Nishimura, Aug 25, 2015
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    • "If we restrict our analysis to the identification of the last neuronal relays, i.e., interneurons and pyramids, many ex vivo experiments from our group have clearly demonstrated that distinct subclasses of interneurons containing VIP, NOS, SOM, and NPY control directly the tone of the smooth muscles of the arterioles (Cauli et al., 2004; Rancillac et al., 2006). Indeed, smooth muscles of the penetrating arterioles are ideally localized to be the main regulators of blood flow and pressure in the cortical cortex (Hillman, 2007; Nishimura et al., 2007). This regulation occurs at the precapillary level through sphincters that are involved in a localized control of capillary tone (Peppiatt et al., 2006; Attwell et al., 2010; Hamilton et al., 2010). "
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    • "This suggests that, the deeper a vascular segment is situated, the larger is the number of feeding arteries and so the possible compensation. In consequence, the drastic effects on blood speed observed in several generations of branches downstream of a clotobstructed penetrating arteriole, when an experimental approach was used (Nishimura et al., 2007), may not apply to the whole vessel network, since the experimental exploration is technically limited to the upper part of the cortex. Interestingly, infarct volumes generated by occlusion of intra-cortical arterioles do not present a regular cylindrical shape around the damaged arteriole, but a rather conical shape having its base in the upper cortical layers (Blinder et al., 2010). "
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    • "However, the parameters of pressure/flow were not tightly controlled. The effects of flow on vascular reactivity has also been evaluated under in vivo conditions (Takano et al. 2006; Nishimura et al. 2007), in larger vessels (Shapiro et al. 1971) as well as in excised parenchymal arterioles of greater diameters (>60 μm) (Shimoda et al. 1996, 1998; Bryan et al. 2001a; Horiuchi et al. 2001, 2002; Cipolla et al. 2004, 2009; Cipolla & Bullinger, 2008; Toth et al. 2011). As the effects of flow on vessel diameter are dependent on the calibre of the vessel, understanding the effects of flow on pre-capillary parenchymal arterioles in situ is essential, and forms the basis for the development of this novel experimental approach. "
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