Signaling through the ERK1/2 pathway is crucial for visual cortical plasticity during development. A detailed understanding of ERK mode of action in cortical plasticity is precluded by the lack of knowledge of the subcellular localization of activated ERK in physiological conditions. Previous work has shown that visual stimulation activates ERK in pyramidal neurons of the visual cortex. To investigate whether visual stimulation can activate ERK in specific subcellular compartments, we used electron microscopic immunocytochemistry with antibodies specific for the dually-phosphorylated forms of ERK1 and ERK2 (pERK). We immunolabelled the primary visual cortex of mice that had been placed in complete darkness for three days at the beginning of the critical period (P23-P27). Some of the mice (control group) were anesthetized while still in darkness and perfused. The other animals were perfused after exposure to a normally illuminated environment for 15 min. Preembedding electron microscopy revealed the presence of pERK-IR in the apical dendrites and nucleus of cortical pyramidal neurons. The IR extended into individual dendritic spines and was found in close proximity of postsynaptic densities, whereas labelling of presynaptic boutons was observed only occasionally. Quantitative analysis of pERK-IR in layers 2-3 revealed an almost three-fold increase in the amount of pERK-immunopositive spines in light-exposed compared to dark-reared mice. These data show that activation of ERK with physiological stimuli in vivo causes a nuclear localization of pERK staining as well as a persistent presence of pERK at postsynaptic sites of axospinous junctions.
Localization of activated ERK in dendritic spines of cortical pyramidal neurons after visual stimulation
BOGGIO, ELENA MARIA;SASSOE' POGNETTO, Marco;GIUSTETTO, Maurizio
2004-01-01
Abstract
Signaling through the ERK1/2 pathway is crucial for visual cortical plasticity during development. A detailed understanding of ERK mode of action in cortical plasticity is precluded by the lack of knowledge of the subcellular localization of activated ERK in physiological conditions. Previous work has shown that visual stimulation activates ERK in pyramidal neurons of the visual cortex. To investigate whether visual stimulation can activate ERK in specific subcellular compartments, we used electron microscopic immunocytochemistry with antibodies specific for the dually-phosphorylated forms of ERK1 and ERK2 (pERK). We immunolabelled the primary visual cortex of mice that had been placed in complete darkness for three days at the beginning of the critical period (P23-P27). Some of the mice (control group) were anesthetized while still in darkness and perfused. The other animals were perfused after exposure to a normally illuminated environment for 15 min. Preembedding electron microscopy revealed the presence of pERK-IR in the apical dendrites and nucleus of cortical pyramidal neurons. The IR extended into individual dendritic spines and was found in close proximity of postsynaptic densities, whereas labelling of presynaptic boutons was observed only occasionally. Quantitative analysis of pERK-IR in layers 2-3 revealed an almost three-fold increase in the amount of pERK-immunopositive spines in light-exposed compared to dark-reared mice. These data show that activation of ERK with physiological stimuli in vivo causes a nuclear localization of pERK staining as well as a persistent presence of pERK at postsynaptic sites of axospinous junctions.
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