1. Ontogeny of voltage-sensitive calcium channel α1A and α1E subunit expression and synaptic function in rat central nervous system
- Author
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Meacham, Connie A., White, Lori D., Barone Jr, Stanley, and Shafer, Timothy J.
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CALCIUM channels , *IMMUNOHISTOCHEMISTRY - Abstract
Immunohistochemical expression in the neocortex, hippocampus and cerebellum of the α1A or α1E subunit of the voltage-sensitive Ca2+ channel was examined in Long–Evans hooded rats on gestational day 18 and postnatal days 1, 4, 7, 10, 14, 21, 90, 360 and 720. On gestational day 18 and postnatal day 1, α1A immunoreactivity was more dense in the neocortex and hippocampus than the cerebellum. By postnatal day 7, levels of α1A immunoreactivity increased dramatically in the cerebellum, while in neocortex, α1A immunoreactivity became more sparse, which approached the more diffuse pattern of cellular staining in the mature brain. Expression of α1E in the neocortex, hippocampus and cerebellum was much less dense than α1A between gestational day 18 and postnatal day 4. There was also significant α1E immunoreactivity in the mossy fibers of the hippocampus and in dendrites of Purkinje cells of the cerebellum. Depolarization-dependent 45Ca2+ influx was examined in rat brain synaptosomes on postnatal days 4, 7, 10, 14, 21 and >60. In neocortical and hippocampal synaptosomes, 45Ca2+ influx increased steadily with age and reached adult levels by postnatal day 10. In cerebellar synaptosomes, 45Ca2+ influx was constant across all ages, except for a spike in activity which was observed on postnatal day 21. In neocortical and hippocampal synaptosomes, 100 nM ω-conotoxin MVIIC significantly inhibited 45Ca2+ influx on postnatal day 10 and 14, respectively, or after. In cerebellar synaptosomes, influx was inhibited by ω-conotoxin MVIIC only on postnatal day 10 or prior. On postnatal day 7, 45Ca2+ influx was not inhibited in neocortical and hippocampal synaptosomes by a combination of 10 μM nifedipine, 1 μM ω-conotoxin GVIA and 1 μM ω-conotoxin MVIIC, suggesting that an ‘insensitive’ flux predominates at this age. Overall, the results suggest that expression of voltage-sensitive Ca2+ channels during development is dynamic and is important in central nervous system development. [Copyright &y& Elsevier]
- Published
- 2003
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