Activity-dependent modifications of synaptic transmission in the developing visual cortex require intracellular signalling through the activation of the ERK pathway. However, it is still unclear whether and how ERK activation might be targeted to subcellular compartments such as dendritic spines and axon terminals in response to physiological stimuli. To test this hypothesis, we used an antibody specific for activated ERK (pERK) to immunolabel the primary visual cortex of both mice and rats after visual stimulation. Ultrastructural localization of pERK was achieved using a preembedding immunogold technique with Nanogold labelling reagents. In light exposed animals, pERK-immunoreactivity (IR) was found in apical dendrites, cell body and the nucleus of cortical pyramidal neurons of layers II-III. At synaptic sites, immunogold labelling decorated individual dendritic spines and was also found in presynaptic terminals establishing axospinous synapses. Quantitative analysis in layers I and II-III revealed that light exposure induced an almost three-fold increase in the number of pERK positive dendritic spines as well as a two-fold increase of labelled presynaptic boutons. Moreover, synaptic ERK activation was evident 2.5 minutes after the onset of visual stimulation and returned to baseline after about 40 minutes. Finally, postsynaptic labelling was mainly found near nonsynaptic membranes and within the core of dendritic spines, suggesting that pERK may modulate the activity of membrane associated proteins as well as cytoplasmic substrates. These data show that activation of ERK in vivo causes a nuclear localization of pERK staining as well as a persistent presence of pERK at synaptic sites of axospinous junctions. Thus, once induced by synaptic stimulation pERK may regulates new genes expression and it may act to phosphorylate target proteins of both the pre- and post-synaptic compartments. Support contributed by: MIUR, Regione Piemonte, Compagnia di San Paolo.
ERK activation can be induced in synaptic contacts of cortical visual neurons by physiological stimuli
BOGGIO, ELENA MARIA;SASSOE' POGNETTO, Marco;GIUSTETTO, Maurizio
2006-01-01
Abstract
Activity-dependent modifications of synaptic transmission in the developing visual cortex require intracellular signalling through the activation of the ERK pathway. However, it is still unclear whether and how ERK activation might be targeted to subcellular compartments such as dendritic spines and axon terminals in response to physiological stimuli. To test this hypothesis, we used an antibody specific for activated ERK (pERK) to immunolabel the primary visual cortex of both mice and rats after visual stimulation. Ultrastructural localization of pERK was achieved using a preembedding immunogold technique with Nanogold labelling reagents. In light exposed animals, pERK-immunoreactivity (IR) was found in apical dendrites, cell body and the nucleus of cortical pyramidal neurons of layers II-III. At synaptic sites, immunogold labelling decorated individual dendritic spines and was also found in presynaptic terminals establishing axospinous synapses. Quantitative analysis in layers I and II-III revealed that light exposure induced an almost three-fold increase in the number of pERK positive dendritic spines as well as a two-fold increase of labelled presynaptic boutons. Moreover, synaptic ERK activation was evident 2.5 minutes after the onset of visual stimulation and returned to baseline after about 40 minutes. Finally, postsynaptic labelling was mainly found near nonsynaptic membranes and within the core of dendritic spines, suggesting that pERK may modulate the activity of membrane associated proteins as well as cytoplasmic substrates. These data show that activation of ERK in vivo causes a nuclear localization of pERK staining as well as a persistent presence of pERK at synaptic sites of axospinous junctions. Thus, once induced by synaptic stimulation pERK may regulates new genes expression and it may act to phosphorylate target proteins of both the pre- and post-synaptic compartments. Support contributed by: MIUR, Regione Piemonte, Compagnia di San Paolo.
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