Behavioral Assessment of Visual Function via Optomotor Response and Cognitive Function via Y-Maze in Diabetic Rats

Summary

Neural degeneration in both eyes and brain as a result of diabetes can be observed through behavioral tests carried out on rodents. The Y-maze, a measure of spatial cognition, and the optomotor response, a measure of visual function, both provide insight into potential diagnoses and treatments.

Abstract

The optomotor response and the Y-maze are behavioral tests useful for assessing visual and cognitive function, respectively. The optomotor response is a valuable tool to track changes in spatial frequency (SF) and contrast sensitivity (CS) thresholds over time in a number of retinal disease models, including diabetic retinopathy. Similarly, the Y-maze can be used to monitor spatial cognition (as measured by spontaneous alternation) and exploratory behavior (as measured by a number of entries) in a number of disease models that affect the central nervous system. Advantages of the optomotor response and the Y-maze include sensitivity, speed of testing, the use of innate responses (training is not needed), and the ability to be performed on awake (non-anesthetized) animals. Here, protocols are described for both the optomotor response and the Y-maze and examples of their use shown in models of Type I and Type II diabetes. Methods include preparation of rodents and equipment, performance of the optomotor response and the Y-maze, and post-test data analysis.

Introduction

Over 463 million people live with diabetes, making it one of the largest global disease epidemics¹. One of the serious complications that arises from diabetes is diabetic retinopathy (DR), a leading cause of blindness for working-age American adults². In the next 30 years, the percentage of the population at risk for DR is projected to double, so it is crucial to find new ways of diagnosing DR in its earlier stages to prevent and mitigate DR development³. DR has conventionally been thought to be a vascular disease^4,5,

Protocol

All procedures were approved by the Atlanta Veterans Affairs Institutional Animal Care and Use Committee and conformed to the National Institutes of Health guide for the care and use of laboratory animals (NIH Publications, 8^th edition, updated 2011).

1. The optomotor response (OMR)

1. Set up the OMR apparatus (details on apparatus and software in Table of Materials)
   1. Choose the appropriate-sized platform for the rodent: mouse, rat, or large/impaired rat (Figure 1A).
   2. Open the OMR software, which should open to a window with several tabs of options and a....

Results

The OMR is considered successful if spatial frequency and contrast sensitivity thresholds can be obtained from a rodent. Here, the use of the OMR to assess spatial frequency is illustrated in naïve control Brown-Norway and Long-Evans rats, both young (3–6 months) and aged (9–12 months). Brown-Norway rats typically show a higher baseline spatial frequency than Long-Evans rats. Additionally, an aging effect on spatial frequency was observed in the Long-Evans rats (Figure 3A). Data were analyze.......

Discussion

The OMR and the Y-maze allow for the non-invasive assessment of visual function and cognitive function deficits in rodents over time. In this protocol, the OMR and the Y-maze were demonstrated to track visual and cognitive deficits in rodent models of diabetes.

Critical steps in the protocol

The OMR

Some important points to consider when performing the OMR to assess visual function are the testing parameters used, experim.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
OptoMotry HD	CerebralMechanics Inc.		OMR apparatus & software
Timer	Thomas Scientific	810029AR
Y-Maze apparatus	San Diego Instruments	7001-043	Available specifically for rats