title: Is adenosine a modulator of peripheral vasoconstrictor responses?
abstract: BACKGROUND
  Local vasoconstrictor reflexes, the vascular myogenic response (VMR) and the veno-arterial reflex (VAR) are necessary for the maintenance of regional blood flow and systemic arterial blood pressure during orthostatic stress. Their molecular mechanism is unknown. We postulated that adenosine is involved in the activation of these local reflexes.
  
  
  METHODS
  This hypothesis was tested in 10 healthy male volunteers (age 29 ± 3 years, BMI 24 ± 1 kg/m(2)). We used veno-occlusive plethysmography method for the assessment of forearm arterial blood flow at baseline and upon causing local venous congestion by inflating a second cuff to 40 mmHg for 4 min (VAR) and during placement of the forearm 40 cm below cardiac level for 4 min (VMR). These measurements were repeated after local infusion of either saline or aminophylline, non-selective adenosine blockers, using the Bier block method.
  
  
  RESULTS
  Rest baseline forearm blood flow was comparable in both arms. Saline did not affect the baseline forearm blood flow. However, aminophylline causes a significant increase in baseline forearm blood flow of 34 ± 6 % (p = 0.002). VAR demonstrated a decrease in forearm blood flow of 49 ± 4.5 % and after saline infusion it remained unchanged, 49 ± 5 % (p = 0.92). However, aminophylline causes significant decrease in the VAR by 35 ± 3 % (p = 0.02). But, both, saline and aminophylline did not affect the VMR.
  
  
  CONCLUSIONS
  Arterial vasoconstriction triggered by venous congestion, which is the veno-arterial reflexis seems to be modulated by adenosine, at least partially. This "sensory" reflex requires further pharmacologic physiologic investigation.
authors: Pain Institute, Tel Aviv Medical Center and Sackler Faculty of Medicine, TAU, Tel Aviv, Israel.|Recanati Autonomic Dysfunction Center Tel Aviv Medical Center and Sackler Faculty of Medicine, TAU, Tel Aviv, Israel.
authors: Lior
authors: L
authors: Dayan
authors: Pain Institute, Tel Aviv Medical Center and Sackler Faculty of Medicine, TAU, Tel Aviv, Israel.
authors: Silviu
authors: S
authors: Brill
authors: Pain Institute, Tel Aviv Medical Center and Sackler Faculty of Medicine, TAU, Tel Aviv, Israel.|Recanati Autonomic Dysfunction Center Tel Aviv Medical Center and Sackler Faculty of Medicine, TAU, Tel Aviv, Israel.
authors: Uri
authors: U
authors: Hochberg
authors: Recanati Autonomic Dysfunction Center Tel Aviv Medical Center and Sackler Faculty of Medicine, TAU, Tel Aviv, Israel. jacobgi@tlvmc.gov.il.|Internal Medicine Department, Tel Aviv Medical Center and Sackler Faculty of Medicine, TAU, Tel Aviv, Israel. jacobgi@tlvmc.gov.il.|Department of Medicine and Physiology, Faculty of Medicine, Weizmann 6, 64239, Tel Aviv, Israel. jacobgi@tlvmc.gov.il.
authors: Giris
authors: G
authors: Jacob
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D000328:Adult; D000628:Aminophylline / Q000494:pharmacology; D005542:Forearm / Q000098:blood supply; D006801:Humans; D008297:Male; D010991:Plethysmography; D012018:Reflex / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*
chemical_list: D000628:Aminophylline; D000241:Adenosine
keywords: Adenosine; Myogenic; Vascular; Veno-arteiolar reflex