title: The origin of the biphasic flow response to local heat in skin.
abstract: OBJECTIVE
  Although it is well established that the application of local heat causes a biphasic increase in skin blood flow, the responsible microvessels have not been identified.
  
  
  METHODS
  A bifurcating network of arterioles (1st-5th orders, 60-15 mum, n = 10 per group) of the intact, unanesthetized, translucent bat wing were visualized on a transparent heat plate via intravital microscopy. Similar to previous bat wing studies, plate temperature was set at 25 degrees C for 10 min then increased to 37 degrees C for 20 min. Vessel diameter and red blood cell velocity were recorded and used to calculate resistance and blood flow.
  
  
  RESULTS
  The average flow response in arterioles was biphasic (p = 0.02) and proportional to the temporal decrease in total resistance calculated from 1st-5th order arterioles. Metarteriole (i.e., 5th order arteriole) resistance had the greatest impact on total resistance (-67.0 +/- 20.7%) and exhibited a biphasic trend that was opposed by temporal changes in resistance of 1st-4th order arterioles.
  
  
  CONCLUSIONS
  Metarterioles are not only necessary but sufficient to explain the origin of the biphasic flow response in skin blood flow.
authors.affiliation: The Michael E. DeBakey Institute, Texas A&M University, College Station, Texas, USA.
authors.forename: R Jay
authors.initials: RJ
authors.lastname: Widmer
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Laurinec
authors.forename: Missy F
authors.initials: MF
authors.lastname: Young
authors.forename: M Waqar
authors.initials: MW
authors.lastname: Mohiuddin
authors.forename: Glen A
authors.initials: GA
authors.lastname: Laine
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Quick
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D002685:Chiroptera / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D012039:Regional Blood Flow / Q000502:physiology; D012867:Skin / Q000098:blood supply*; D014921:Wings, Animal / Q000098:blood supply*