title: Vasopressin facilitates presynaptic sympathetic nerve activity in humans.
abstract: OBJECTIVE
  It was the objective of this study to investigate whether a facilitatory role of vasopressin (AVP) on sympathetic nerve activity can be demonstrated in humans at the peripheral level.
  
  
  METHODS
  Eight subjects (32 +/- 2.3 years) participated in this study. Forearm blood flow (FABF) was measured using the venous occlusion plethysmography model. Each session was performed in the presence of a continuous infusion (into the brachial artery) of AVP in sub-pressor dosage of 0.008 ng/kg per min, or NaCl 0.9%. Using lower-body negative pressure (LBNP) (-10, -20 and -30 mmHg) the combined pre- and postsynaptic action of AVP on the sympathetic nervous system was investigated. This was followed by a second protocol in which the possible postsynaptic effects of AVP were evaluated with intra-arterial infused norepinephrine (NE).
  
  
  RESULTS
  The baseline FABF was 5.2 +/- 0.6 ml/100 ml per min. After infusion of AVP (0.008 ng/kg per min), the FABF remained unchanged at a flow of 5.5 +/- 0.6 ml/100 ml per min (P = 0.26). LBNP caused a pressure-dependent decrease in FABF (25.6 +/- 4.4, 29.0 +/- 6.1 and 38.6 +/- 6.9%, for -10, -20 and -30 mmHg, respectively). AVP significantly enhanced the FABF responses to lower-body negative pressures (38.0 +/- 8.6, 49.3 +/- 5.1 and 58.9 +/- 6.3%, respectively (P = 0.014). NE caused a dose-dependent vasoconstriction by 3.1 +/- 4.6, 17.0 +/- 4.3 and 23.2 +/- 4.9%, at dosages of 10, 20 and 40 pg/min, respectively, unaffected by AVP (P = 0.91).
  
  
  CONCLUSIONS
  We conclude that AVP can facilitate vasoconstriction mediated by the peripheral sympathetic nervous system at the presynaptic level in humans.
authors.affiliation: Department of Pharmacotherapy, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. J.O.Streefkerk@amc.uva.nl
authors.forename: Jörn O
authors.initials: JO
authors.lastname: Streefkerk
authors.forename: Jippe C
authors.initials: JC
authors.lastname: Balt
authors.forename: Gert A
authors.initials: GA
authors.lastname: van Montfrans
authors.forename: Johan J
authors.initials: JJ
authors.lastname: van Lieshout
authors.forename: Martin
authors.initials: M
authors.lastname: Pfaffendorf
authors.forename: Pieter A
authors.initials: PA
authors.lastname: van Zwieten
mesh_terms: D000328:Adult; D001127:Arginine Vasopressin / Q000008:administration & dosage*; D001916:Brachial Artery / Q000294:innervation / Q000502:physiology; D005260:Female; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D009638:Norepinephrine / Q000008:administration & dosage; D010991:Plethysmography; D017729:Presynaptic Terminals / Q000187:drug effects*; D012039:Regional Blood Flow / Q000187:drug effects*; D013564:Sympathetic Nervous System / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000008:administration & dosage*
chemical_list: D014662:Vasoconstrictor Agents; D001127:Arginine Vasopressin; D009638:Norepinephrine