Matrix metalloproteinases (MMPs) are capable of remodeling extracellular matrix and have been implicated in synaptic plasticity, learning and memory. In particular, upregulation of gelatinases (MMP-2 and 9) accompanies long-term potentiation (LTP) in hippocampal Schaeffer collateral-CA1 pathway. However, the role of gelatinases in synaptic plasticity in other hippocampal pathways remains unknown. Recently, we have found that MMPs blockade by FN-439 abolishes LTP consolidation in the dentate gyrus-CA3 (DG-CA3) projection (where LTP expression is presynaptic, Wójtowicz and Mozrzymas 2010). To address the involvement of gelatinases in the plasticity of this pathway, we have combined high resolution in situ zymography with DQ-gelatin (DQ-G) and immunofluorescence in hippocampal sections from slices used in electrophysiological experiments. LTP was evoked by high frequency stimulation (HFS, 4×100 Hz) while baseline (control) stimulation was applied at 0.1 Hz. Following fixation, slices were cut into thin sections, treated with DQ-G and stained against a neuronal marker MAP-2. The intensity of DQ-G fluorescence was quantified for MAP-2 positive neurons using confocal microscopy. Computer- and visually-guided analysis of cytoplasm and proximal dendrites of target hilar and CA3 neurons revealed that LTP induction was associated with a significant increase in DQ-G fluorescence (30% and 35% increase, respectively, n=6 animals, p<0.05). Importantly, cytoplasmic DQ-G fluorescence profile corroborated with immunoreactivity for MMP-9. The overall DQ-G fluorescence signal in MAP-2 and GFAP-negative extracellular space did not differ between control and HFS-stimulated preparations (n=6 animals, p=0.89). In conclusion, we provide evidence that stimulation pattern that evokes LTP in the DG-CA3 pathway, induces a significant up regulation of gelatinases in the cytoplasm of postsynaptic hilar and CA3 neurons. Support: Grants NN401541540 and UDA-POKL.04.01.01-00-010/08-01.
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