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Intraocular CNTF reduces vision in normal rats in a dose-dependent manner
Trevor J McGill1, Glen T Prusky, Robert M Douglas
1Canadian Centre for Behavioural Neuroscience, The University of Lethbridge, Lethbridge, Alberta, Canada.
Investigative Ophthalmology & Visual Science
|December 7, 2007
Summary
Intraocular delivery of Ciliary Neurotrophic Factor (CNTF) can impair visual function in normal rats at high doses. However, lower doses may offer protection against retinal damage without compromising vision.
Area of Science:
- Ophthalmology
- Neuroscience
- Retinal Biology
Background:
- Ciliary Neurotrophic Factor (CNTF) is recognized for its neuroprotective properties in retinal degeneration models.
- Previous studies indicate CNTF can lead to reduced electroretinogram (ERG) amplitudes.
- Understanding CNTF's impact on normal visual function is crucial for its therapeutic application.
Purpose of the Study:
- To investigate the effects of intraocular CNTF delivery on the visual function of normal rats.
- To assess dose-dependent effects of CNTF on retinal function and visual acuity.
Main Methods:
- Intravitreous or subretinal adeno-associated virus-vectored CNTF (AAV-CNTF) injections were administered to adult Long-Evans rats.
- Full-field scotopic and photopic electroretinogram (ERG) amplitudes were measured.
- Optokinetic response (OKR) spatial frequency thresholds and visual acuity were assessed.
Main Results:
- High-dose intraocular CNTF significantly reduced ERG amplitudes and OKR thresholds by 45-70% within 6 days, with slow recovery over 90-100 days.
- AAV-CNTF delivery led to approximately 50% reduction in OKR thresholds and visual acuity for at least 6 months.
- Photoreceptor loss was observed in some AAV-CNTF-injected eyes, but therapeutic doses were identified that preserve ERG responses.
Conclusions:
- Intraocular CNTF can transiently impair visual function in normal rats, particularly at high doses.
- Lower, potentially therapeutic doses of CNTF may preserve photoreceptors without causing significant visual impairment.
- Careful dose-optimization is necessary for safe and effective CNTF-based therapies for retinal diseases.
