Conditional Intrinsic Voltage Oscillations in Mature Vertebrate Neurons Undergo Specific Changes in Culture

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Abstract
Although intrinsic neuronal properties in invertebrates are well known to undergo specific adaptive changes in culture, long-term adaptation of similar properties in mature vertebrate neurons remain poorly understood. To investigate this, we used an organotypic slice preparation from the spinal cord of adult turtles maintainable for several weeks in culture conditions. N-methyl-d-aspartate (NMDA)-induced-tetrodotoxin (TTX)-resistant voltage oscillations in motoneurons were ∼10 times faster in culture than in acute preparations. Oscillations in culture were abolished by NMDA receptor antagonists or by high extracellular Mg2+ concentrations. However, in contrast with results from motoneurons in the acute slice, NMDA-induced oscillations in culture did not depend on CaV1.3 channel activation as they still remained after nifedipine application. Other CaV1.3 channel-mediated properties such as metabotropic receptor-induced oscillations and plateau potentials failed to be induced in culture. This study shows that changes specifically affecting CaV1.3 channel contribution to intrinsic oscillatory property expression may occur in culture. The results contribute also to understanding further the potential for plasticity of mature vertebrate neurons.