Related Experiment Videos
GAP-43 in the cat visual cortex during postnatal development
H McIntosh1, N Daw, D Parkinson
1Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110.
Insights
Growth associated protein 43 (GAP-43) levels in cat brains decrease with age, correlating with developmental plasticity. Visual deprivation did not affect GAP-43 during the critical period, suggesting its decline indicates remaining plasticity.
Area of Science:
- Neuroscience
- Developmental Biology
- Molecular Biology
Background:
- Growth associated protein 43 (GAP-43) is implicated in neural plasticity.
- The critical period for plasticity in the visual cortex is a key developmental stage.
- Understanding GAP-43's role can illuminate the mechanisms of critical period plasticity.
Purpose of the Study:
- To investigate the relationship between GAP-43 expression and the duration of the critical period for plasticity in the cat visual cortex.
- To examine the effect of visual deprivation on GAP-43 levels during postnatal development.
- To determine if GAP-43 levels can serve as an index of remaining plasticity.
Main Methods:
- Quantification of GAP-43 levels using immunoassay in cat visual cortex, motor cortex, somatosensory cortex, and cerebellum at various postnatal ages.
- Assessment of GAP-43 levels following monocular deprivation for 2-7 days, ending at 27 or 35 days of age.
- Correlation analysis between membrane-associated GAP-43 concentrations and developmental events.
Main Results:
- GAP-43 levels were high at 5 days old across all brain regions, declining significantly by 60 days and continuing to decrease slowly into adulthood.
- Monocular deprivation did not alter total membrane GAP-43 levels in the visual cortex.
- Pre-40 days GAP-43 concentrations correlated with visual cortex development, while the post-40 days decline suggested ongoing plasticity.
Conclusions:
- GAP-43 concentrations in the cat visual cortex decrease significantly during postnatal development.
- Visual deprivation does not affect GAP-43 levels during the critical period, indicating it may not be directly involved in ocular dominance plasticity.
- The declining levels of membrane-associated GAP-43 after 40 days of age may serve as an indicator of plasticity persistence beyond the critical period's peak.
Abstract:
GAP-43 levels have been determined by immunoassay in cat visual cortex during postnatal development to test the idea that GAP-43 expression could be related to the duration of the critical period for plasticity. For comparison, GAP-43 levels have also been assayed in primary motor cortex, primary somatosensory cortex, and cerebellum at each age. GAP-43 levels were high in all regions at 5 d (with concentrations ranging from 7-10 ng/microgram protein) and then declined 60-80% by 60 d of age. After 60 d of age, GAP-43 concentrations in each region continued a slow decline to adult values, which ranged from 0.5-2 ng/microgram protein. To test for the involvement of GAP-43 in ocular dominance plasticity during the critical period, the effect of visual deprivation on GAP-43 levels was investigated. Monocular deprivation for 2-7 d, ending at either 27 or 35 d of age, had no effect on total membrane levels of GAP-43. The concentrations of membrane-associated GAP-43 prior to 40 d of age correlate with events that occur during postnatal development of the cat visual cortex. However, the slow decline in membrane-associated GAP-43 levels after 40 d of age may be an index of relative plasticity remaining after the peak of the critical period.