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Functional development of the visual system in normal and protein-deprived rats. IX. Visual evoked response in young
1Department of Ophthalmology, Gothenburg University, Sweden.
Insights
Protein deprivation in rats delays visual evoked response (VER) development, impacting both the visual cortex and the dorsal lateral geniculate nucleus (dLGN). This developmental delay may contribute to later visual cortex functional deficits.
Area of Science:
- Neuroscience
- Developmental Biology
- Nutritional Science
Background:
- Early life nutrition significantly influences neurodevelopment.
- Protein deprivation (PD) is known to affect brain development, but its specific impact on the visual system requires further elucidation.
Purpose of the Study:
- To investigate the effects of early postnatal protein deprivation on the maturation of the visual evoked response (VER) in rats.
- To determine if protein deprivation alters the timing and progression of visual system development.
Main Methods:
- Recorded visual evoked responses (VER) to light-flash stimulation in the dorsal lateral geniculate nucleus (dLGN) and visual cortex of control and protein-deprived rats.
- Analyzed changes in VER latencies during early postnatal development (up to 26/27 days).
Main Results:
- Protein-deprived rats exhibited delayed development of the cortical VER, with increased latencies (10-15 ms) at 17 days.
- The developmental trajectory of VER latencies was altered, showing a delay of approximately 3 days in PD rats.
- At later stages (26/27 days), both cortical and dLGN VER latencies remained elevated in PD rats, suggesting widespread visual system impact.
Conclusions:
- Early postnatal protein deprivation significantly delays and distorts the normal developmental maturation of the rat visual system.
- These neurodevelopmental alterations in the visual pathway may underlie functional deficits observed in the visual cortex of adult protein-deprived rats.
Abstract:
Changes in latencies of the visual evoked response (VER) during early post-natal development were examined in protein-deprived (PD) rats. The evoked response to light-flash stimulation was recorded in the dorsal lateral geniculate nucleus (dLGN) and on the surface of the visual cortex. In control rats, latencies of the cortical VER decreased rapidly up to 20 days and slowly thereafter. In PD rats, the latencies of the cortical VER were increased by 10-15 ms at 17 days; the developmental decrease was delayed by approximately 3 days. After 20 days, PD rats also went into a phase with slow decrease of the latencies, and the onset latency of the cortical VER was still increased by some 10 ms at 26/27 days. At this age, PD rats showed an increase in the latencies of the VER in the dLGN which was of similar magnitude to that in the cortical VER, indicating that alterations were more marked in the peripheral parts of the visual system at this stage of development. The findings are in agreement with previous studies indicating that there is a delay of visual system development in PD rats before 20 days. A maturational event which turns rapid into slow development at approximately 20 days in both C and PD rats turns this delay into a distortion of development. The delays and distortions of visual system development may be one causative factor for the functional deficit present in the visual cortex of adult PD rats.