title: Retinal Vessel Diameter Responses to Central Electrical Stimulation in the Rat: Effect of Nitric Oxide Synthase Inhibition.
abstract: Recent histological data suggest autonomic innervation of the central retinal artery. In the present study, we investigated the effect of electrical brain stem stimulation at the superior salivatory nucleus (SSN) on the retinal vessel diameter in rats and whether nitric oxide mediates a possible effect.
  
  
  
  Sprague-Dawley rats (n = 12) were anesthetized using pentobarbital sodium (50 mg/kg intraperitoneally). The animals were artificially ventilated and the femoral artery and vein were cannulated for blood pressure measurement and drug administration. After a craniotomy was performed, a unipolar stainless steel electrode was inserted into the brainstem at the coordinates of the SSN. Stimulations were performed at 20 Hz, 9 μA, 1 ms pulse duration and 200 pulses. Retinal vessel diameters were measured continuously with the Imedos DVA-R, a noncontact fundus camera for rats with image analysis software. After control measurements, L-NAME, a nonspecific inhibitor of NO synthase, was applied intravenously (10 mg/kg), and the SSN stimulations were repeated.
  
  
  
  Stimulation at the SSN coordinates increased the retinal arterial diameter by 6.41% ± 1.65% and the venous diameter by 3.48% ± 1.93% (both P < 0.05). Application of L-NAME reduced the arterial response significantly to 2.93% ± 0.91%, but did not change the venous response. Mean arterial pressure, carotid blood flow, and heart rate remained unaltered (by the stimulation).
  
  
  
  The present study demonstrates that the retinal circulation reacts to electric stimulation at the SSN coordinates in rats. Nitric oxide is involved in the response, but it is not the sole neurotransmitter.
authors: Clemens A
authors: CA
authors: Strohmaier
authors: Karolina
authors: K
authors: Motloch
authors: Christian
authors: C
authors: Runge
authors: Andrea
authors: A
authors: Trost
authors: Barbara
authors: B
authors: Bogner
authors: Alexandra
authors: A
authors: Kaser-Eichberger
authors: Falk
authors: F
authors: Schrödl
authors: Markus
authors: M
authors: Lenzhofer
authors: Herbert A
authors: HA
authors: Reitsamer
mesh_terms: D000818:Animals; D004558:Electric Stimulation / Q000379:methods*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D010275:Parasympathetic Nervous System / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000502:physiology; D012171:Retinal Vessels / Q000166:cytology / Q000294:innervation* / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester