September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Vascular and electroretinogram responses to hypercapnia and hyperoxia in the Streptozotocin diabetic rat
Author Affiliations & Notes
  • Joe Wang
    Optometry and Vision Science, The University of Melbourne, Burwood East, Victoria, Australia
  • Zheng He
    Optometry and Vision Science, The University of Melbourne, Burwood East, Victoria, Australia
  • Andrew Ian Jobling
    Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
  • Erica Fletcher
    Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
  • Algis J Vingrys
    Optometry and Vision Science, The University of Melbourne, Burwood East, Victoria, Australia
  • Bang V Bui
    Optometry and Vision Science, The University of Melbourne, Burwood East, Victoria, Australia
  • Footnotes
    Commercial Relationships   Joe Wang, None; Zheng He, None; Andrew Jobling, None; Erica Fletcher, None; Algis Vingrys, None; Bang Bui, None
  • Footnotes
    Support  Australian Research Council Future Fellowship FT130100388
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 5421. doi:
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    • Get Citation

      Joe Wang, Zheng He, Andrew Ian Jobling, Erica Fletcher, Algis J Vingrys, Bang V Bui; Vascular and electroretinogram responses to hypercapnia and hyperoxia in the Streptozotocin diabetic rat. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5421.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To investigate the effect of O2 and CO2 inhalation (hyperoxia and hypercapnia) on retinal blood vessel calibre and inner retinal function at early stages in the streptozotocin (STZ) model of diabetes.

Methods : Dark Agouti rats aged 8 weeks received intravenous STZ (55mg/Kg, n = 10) or vehicle injection (citrate buffer, n=10). After 4 weeks, Electroretinogram (ERG) and fundus imaging were conducted under general anaesthesia (60:5 mg/Kg Ketamine: Xylazine).
100% O2 and CO2 mix (10% CO2 / 90% room air) were delivered in randomised order for 5min, followed by 5 min recovery. Arterial blood gas was taken to verify hyperoxia and hypercapnia. Retinal vessels were imaged every 10 seconds and analysed using ImageJ (percentage relative to baseline). The scotopic threshold response (STR, -5.01 logcd.s/m2) was recorded every minute during the protocol.

Results : STZ animals developed hyperglycemia compared to controls (25±0.8 vs 7.7±0.3mmol/L, p<0.05). CO2 produced similar hypercapnia between STZ and control animals (PaCO2 +8.0±2.1mmHg vs +10.4±8.0mmHg, p=0.44), but more vasodilation in STZ animals (arteriole 113±1%, venule 112±1%) compared to controls (arteriole 109±6%, venule 109±2%, p<0.01). Arterioles in STZ animals remained dilated for the duration of hypercapnia, while control arteries reconstricted after 2 minutes. O2 produced hyperoxia similarly between the STZ and control groups (PaO2 +254±34 vs (+263±38mmHg, p=0.85) with no difference in vasoconstriction magnitude (STZ arteriole 86±1%; venule 85±1%; control arteriole 87±2%, vein 86±2%, p=0.67). Despite this, STZ animals showed slower venule vasoconstriction during hyperoxia. Hypercapnia produced similar increases in pSTR (Cit 144±13%, STZ 152±16% P=0.49) and nSTR amplitude (Cit 49±12%, STZ 53±11% P=0.89) in both groups of animals. Hyperoxia produced significantly more reduction in pSTR (Cit 90±4%, STZ 81±6% P< 0.01), and significantly more increase in nSTR (Cit 117%±5%, STZ 125±12% P=0.03) in STZ animals compared to citrate controls.

Conclusions : Hypercapnia and hyperoxia produce robust vasodilation and vasoconstriction respectively. Vasodilation is associated with reduction in nSTR and therefore increased pSTR. Vasoconstriction produces a larger nSTR and smaller pSTR. This effect was exaggerated in diabetic animals and may reflect disconnect in the timecourse between arteriole and venule vasoconstriction in STZ rats.

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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