Early inner retinal dysfunction in streptozotocin-induced diabetic rats

Area of Science:

• Ophthalmology
• Neuroscience
• Endocrinology

Background:

• Diabetes mellitus is a systemic disease known to affect ocular tissues, including the retina.
• Previous studies indicate diabetes alters retinal function, with electroretinogram (ERG) showing abnormalities in oscillatory potentials (OPs).
• The specific impact of diabetes on other inner retinal ganglion cell-related responses remains less understood.

Purpose of the Study:

• To systematically evaluate electroretinogram (ERG) changes in rats induced with streptozotocin (STZ) diabetes.
• To assess the time course of retinal functional alterations over 11 weeks post-diabetogenesis.
• To investigate the effects of diabetes on outer and inner retinal function, focusing on ganglion cell responses.

Main Methods:

• Thirty Sprague-Dawley rats were divided into STZ-treated (n=16) and control (n=14) groups.
• Diabetic rats received daily insulin injections; ERGs were recorded at 4, 8, and 11 weeks.
• ERG parameters analyzed included a-wave (outer retina), b-wave, oscillatory potentials (OPs), and scotopic threshold response (STR) (inner retina).

Main Results:

• Photoreceptoral (a-wave) and bipolar cell (b-wave) functions remained largely unaffected by STZ treatment.
• Oscillatory potentials (OPs) showed significant reduction by 8 weeks (-25%, P < 0.05).
• The positive scotopic threshold response (pSTR), dominated by ganglion cells, exhibited significant decreases from 4 weeks (-51%, P < 0.05), while the negative component was unaffected.

Conclusions:

• STZ-induced diabetes leads to significant dysfunction in inner retinal components.
• Retinal ganglion cell function, as indexed by the positive scotopic threshold response (pSTR), is severely impaired early in diabetes.
• These findings highlight the vulnerability of retinal ganglion cells to diabetic complications.