title: Laser speckle contrast imaging reveals large-scale synchronization of cortical autoregulation dynamics influenced by nitric oxide.
abstract: Synchronization of tubuloglomerular feedback (TGF) dynamics in nephrons that share a cortical radial artery is well known. It is less clear whether synchronization extends beyond a single cortical radial artery or whether it extends to the myogenic response (MR). We used LSCI to examine cortical perfusion dynamics in isoflurane-anesthetized, male Long-Evans rats. Inhibition of nitric oxide synthases by N(ω)-nitro-l-arginine methyl ester (l-NAME) was used to alter perfusion dynamics. Phase coherence (PC) was determined between all possible pixel pairs in either the MR or TGF band (0.09-0.3 and 0.015-0.06 Hz, respectively). The field of view (≈4 × 5 mm) was segmented into synchronized clusters based on mutual PC. During the control period, the field of view was often contained within one cluster for both MR and TGF. PC was moderate for TGF and modest for MR, although significant in both. In both MR and TGF, PC exhibited little spatial variation. After l-NAME, the number of clusters increased in both MR and TGF. MR clusters became more strongly synchronized while TGF clusters showed small highly coupled, high-PC regions that were coupled with low PC to the remainder of the cluster. Graph theory analysis probed modularity of synchronization. It confirmed weak synchronization of MR during control that probably was not physiologically relevant. It confirmed extensive and long-distance synchronization of TGF during control and showed increased modularity, albeit with larger modules seen in MR than in TGF after l-NAME. The results show widespread synchronization of MR and TGF that is differentially affected by nitric oxide.
authors.affiliation: Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada;
authors.forename: Nicholas
authors.initials: N
authors.lastname: Mitrou
authors.affiliation: Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts; and.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Scully
authors.affiliation: Department of Medicine and Department of Physiology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Branko
authors.initials: B
authors.lastname: Braam
authors.affiliation: Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts; and.
authors.forename: Ki H
authors.initials: KH
authors.lastname: Chon
authors.affiliation: Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada; wcupples@sfu.ca.
authors.forename: William A
authors.initials: WA
authors.lastname: Cupples
mesh_terms: D000818:Animals; D025461:Feedback, Physiological / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects* / Q000502:physiology; D007678:Kidney Glomerulus / Q000187:drug effects; D007684:Kidney Tubules / Q000187:drug effects; D007834:Lasers; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009399:Nephrons / Q000187:drug effects*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D020318:Rats, Long-Evans; D012079:Renal Circulation / Q000187:drug effects*
chemical_list: D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester
keywords: blood flow; cortex; dynamics; kidney; laser speckle contrast imaging; myogenic response; rats; synchronization; tubuloglomerular feedback