September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Relaxation of retinal arterioles can be induced by veratridine, but not electrical field stimulation
Author Affiliations & Notes
  • Nils Kratholm
    Department of Opthalmology, Aarhus University Hospital, Aarhus, Denmark
  • Ulf Simonsen
    Department of Biomedicine, University of Aarhus, Aarhus, Denmark
  • Peter Skov Jensen
    Department of Opthalmology, Aarhus University Hospital, Aarhus, Denmark
  • Sidse Kringelholt
    Department of Opthalmology, Aarhus University Hospital, Aarhus, Denmark
  • Toke Bek
    Department of Opthalmology, Aarhus University Hospital, Aarhus, Denmark
  • Footnotes
    Commercial Relationships   Nils Kratholm, None; Ulf Simonsen, None; Peter Jensen, None; Sidse Kringelholt, None; Toke Bek, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 116. doi:
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      Nils Kratholm, Ulf Simonsen, Peter Skov Jensen, Sidse Kringelholt, Toke Bek; Relaxation of retinal arterioles can be induced by veratridine, but not electrical field stimulation. Invest. Ophthalmol. Vis. Sci. 2016;57(12):116.

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      © 2017 Association for Research in Vision and Ophthalmology.

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Abstract

Purpose : The retinal vascular system is devoid of autonomic nervous supply and therefore retinal blood flow is autoregulated. However, it is unknown to what extent electrical activity in the retina during the visual process contributes to this flow regulation. The purpose of the present study was to study changes in vascular tone in retinal arterioles during electrical field stimulation (EFS) and in the presence of veratridine, simulating neuronal activity around the vessels.

Methods : Porcine ciliary arteries and retinal arterioles were mounted in a myograph system and the tone was measured during: A) Six series of bipolar field stimulations with a frequency of 1 Hz successively doubled to reach 32 Hz. In each series 30 mA pulses with a duration of 0.3 msec were applied during 20 sec, followed by a resting period of 5 min. B) The successive addition of the Na+ channel opener veratridine in the concentrations: 10-6, 3x10-6, 10-5 and 3x10-5 M. The experiments were repeated after addition of the Na+ blocker tetrodotoxin (TTX). The effect of veratridine was furthermore investigated in the presence of the COX-blocker, ibuprofen (10-5 M), NOS-blocker, L-NAME (10-4 M) and the adenosine-receptor-blocker, 8-PSPT (5x10-5 M). All experiments were conducted both in isolated and non-isolated vessels.

Results : EFS had no significant effect on the tone of retinal arterioles (p>0.66), whereas veratridine showed a concentration dependent relaxation of these vessels (p<0.01). The effect was partially reduced by TTX which depended on the presence of perivascular retinal tissue. Neither ibuprofen, L-NAME nor 8-PSPT affected the veratridine induced relaxation compared to the controls. However, when comparing isolated vessels to vessels with preserved perivascular retinal tissue, relaxation was reduced in the ibuprofen and 8-PSPT group at the second highest and two highest veratridine concentrations, respectively.

Conclusions : EFS has no effect on the tone of porcine retinal arterioles in vitro which may be due to the lack of autonomic nervous supply. The relaxing effect of veratridine does not involve products of cyclo-oxygenase, nitric oxide synthase or the adenosine receptor.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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