Relationships between Intracellular Calcium and Afterhyperpolarizations in Neocortical Pyramidal Neurons

H. J. Abel, J. C.F. Lee, J. C. Callaway, R. C. Foehring

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91 Scopus citations

Abstract

We examined the effects of recent discharge activity on [Ca 2+]i in neocortical pyramidal cells. Our data confirm and extend the observation that there is a linear relationship between plateau [Ca2+]i and firing frequency in soma and proximal apical dendrites. The rise in [Ca2+] activates K+ channels underlying the afterhyperpolarization (AHP), which consists of 2 Ca 2+-dependent components: the medium AHP (mAHP) and the slow AHP (sAHP). The mAHP is blocked by apamin, indicating involvement of SK-type Ca 2+-dependent K+ channels, The identity of the apamin-insensitive sAHP SAHP channel is unknown. We compared the sAHP and the mAHP with regard to: 1) number and frequency of spikes versus AHP amplitude; 2) number and frequency of spikes versus [Ca2+]i; 3) I AHP versus [Ca2+]i. Our data suggest that sAHP channels require an elevation of [Ca2+]i in the cytoplasm, rather than at the membrane, consistent with a role for a cytoplasmic intermediate between Ca2+ and the K+ channels. The mAHP channels appear to respond to a restricted Ca2+ domain.

Original languageEnglish
Pages (from-to)324-335
Number of pages12
JournalJournal of neurophysiology
Volume91
Issue number1
DOIs
StatePublished - Jan 2004

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