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Microencephaly reduces the phosphorylation of the PKC substrate B-50/GAP43 in rat cortex and hippocampus
M Di Luca1, M Cimino, P N De Graan
1Institute of Pharmacological Sciences, University of Milan, Italy.
Abstract:
The administration of the antimitotic agent methylazoxymethanol (MAM) to rats at day 15 of gestation results in a consistent loss of intrinsic neurons primarily in cortex and hippocampus. These animals when adult, show a cognitive impairment, if tested in specific behavioural tasks. B-50/GAP43 is a neuronal phosphoprotein, specific substrate for protein kinase C (PKC) and involved in the development and plasticity of synaptic connections. Since B-50/GAP43 has been implicated in functional modulation of synapses and in the molecular mechanism underlying cognitive processes, we studied the phosphorylation of B-50 in cortex and hippocampus of control and MAM-treated rats. Here we report that B-50 in MAM-treated rats shows a marked reduction in the phosphate incorporation in the areas affected by the prenatal treatment. In situ hybridization studies demonstrate that the mRNA levels for B-50 are not altered in MAM-treated rats and that the relative amount of the protein, as revealed by Western blot analysis, is also not affected in microencephalic rats. These results suggest that microencephalic animals might represent a useful experimental model to study biochemical correlates of cognitive impairment and synaptic plasticity.
Insights
Prenatal exposure to methylazoxymethanol (MAM) impairs cognitive function in rats by reducing B-50/GAP43 phosphorylation in the brain. This microencephalic model offers insights into cognitive deficits and synaptic plasticity.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Cognitive Neuroscience
Background:
- Methylazoxymethanol (MAM) exposure during gestation causes neuronal loss in rat cortex and hippocampus.
- MAM-induced microcephaly in rats leads to cognitive impairments in behavioral tasks.
- B-50/GAP43 is a neuronal phosphoprotein crucial for synaptic development and plasticity, implicated in cognitive processes.
Purpose of the Study:
- To investigate the effect of prenatal MAM exposure on B-50/GAP43 phosphorylation in the cortex and hippocampus of adult rats.
- To explore the relationship between altered B-50/GAP43 phosphorylation and cognitive deficits in a rat model of microcephaly.
Main Methods:
- Administration of methylazoxymethanol (MAM) to pregnant rats at day 15 of gestation.
- Assessment of B-50/GAP43 phosphorylation levels in brain tissue (cortex and hippocampus) using biochemical assays.
- In situ hybridization to analyze B-50 mRNA levels.
- Western blot analysis to determine B-50 protein levels.
Main Results:
- MAM-treated rats exhibited a significant reduction in B-50/GAP43 phosphate incorporation in affected brain regions.
- In situ hybridization revealed no significant alteration in B-50 mRNA levels in MAM-treated rats.
- Western blot analysis showed no change in the overall B-50 protein amount in microencephalic rats.
Conclusions:
- Prenatal MAM exposure leads to reduced B-50/GAP43 phosphorylation, correlating with cognitive impairment.
- The observed changes in phosphorylation, not protein or mRNA levels, suggest a specific biochemical alteration underlying cognitive deficits.
- Microencephalic rats induced by MAM serve as a valuable model for studying the biochemical basis of cognitive impairment and synaptic plasticity.