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Activity-dependent changes in "transplanted" cerebellar cultures
1Neurology Research, Veterans Affairs Medical Center, Portland, Oregon 97201, USA.
Abstract:
Organotypic cerebellar cultures were used to assess the effects of increasing or blocking neuronal activity on circuit reconstruction in an in vitro transplantation model. Granule cells and oligodendrocytes were destroyed and astrocytes were functionally compromised by exposing newborn mouse-derived cerebellar explants to cytosine arabinoside for the first 5 days in vitro. Such cultures were "transplanted" at 9 days in vitro with granule cells and glia and maintained in standard nutrient medium; in medium with the GABA antagonist, picrotoxin, to increase neuronal activity; or with tetrodotoxin and elevated levels of magnesium to block neuronal activity. Transplanted cultures exposed to picrotoxin were not significantly different from control transplanted cultures. Transplanted cultures deprived of neuronal activity had reduced inhibitory synaptogenesis, greater persistence of heterotypical axospinous synapses, and hyperactive cortical spontaneous discharges after recovery from the blockade. Transplantation-induced changes that were not affected included myelination, reduction of sprouted Purkinje recurrent axon collaterals, astrocytic ensheathment of Purkinje cells, reduction of excess Purkinje cell axosomatic synapses, and formation of excitatory parallel fiber-Purkinje cell dendritic spine synapses. The results were consistent with previous studies indicating the necessity of neuronal activity for the full development of inhibitory circuitry, and suggested that neuronal activity is also necessary for the reconstruction of inhibitory circuitry after transplantation.
Insights
Neuronal activity is crucial for reconstructing cerebellar inhibitory circuits after transplantation. Blocking this activity impairs synapse formation and leads to abnormal brain activity, highlighting its importance for circuit repair.
Area of Science:
- Neuroscience
- Cell Biology
- Developmental Biology
Background:
- Organotypic cerebellar cultures provide an in vitro model for studying neural circuit development and repair.
- Cytosine arabinoside treatment in early development can damage cerebellar cells like granule cells and oligodendrocytes, affecting astrocyte function.
Purpose of the Study:
- To investigate the role of neuronal activity in cerebellar circuit reconstruction following transplantation.
- To determine if modulating neuronal activity impacts synapse formation and circuit function after cell transplantation.
Main Methods:
- Utilizing organotypic cerebellar cultures from newborn mice, treated with cytosine arabinoside to induce damage.
- Transplanting granule cells and glia into damaged cultures and manipulating neuronal activity using picrotoxin (GABA antagonist) or tetrodotoxin/magnesium (activity blockers).
- Assessing synaptogenesis, synapse persistence, myelination, and spontaneous cortical discharges post-transplantation and activity modulation.
Main Results:
- Blocking neuronal activity led to reduced inhibitory synaptogenesis and persistent heterotypical axospinous synapses.
- Cultures with blocked neuronal activity exhibited hyperactive cortical spontaneous discharges after recovery.
- Myelination, Purkinje cell ensheathment, and excitatory synapse formation were unaffected by activity modulation.
Conclusions:
- Neuronal activity is essential for the proper development of inhibitory cerebellar circuitry.
- Activity-dependent mechanisms are critical for reconstructing inhibitory circuits after in vitro transplantation.
- These findings underscore the importance of functional neuronal activity for successful neural repair and circuit integration.