Hippocampal 'zipper' slice studies reveal a necessary role for calcineurin in the increased activity of L-type Ca2+ channels with aging

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Abstract

Previous studies have shown that inhibition of the Ca2+-/calmodulin-dependent protein phosphatase calcineurin (CN) blocks L-type voltage sensitive Ca2+ channel (L-VSCC) activity in cultured hippocampal neurons. However, it is not known whether CN contributes to the increase in hippocampal L-VSCC activity that occurs with aging in at least some mammalian species. It is also unclear whether CN's necessary role in VSCC activity is simply permissive or is directly enhancing. To resolve these questions, we used partially dissociated hippocampal "zipper" slices to conduct cell-attached patch recording and RT-PCR on largely intact single neurons from young-adult, mid-aged, and aged rats. Further, we tested for direct CN enhancement of L-VSCCs using virally mediated infection of cultured neurons with an activated form of CN. Similar to previous work, L-VSCC activity was elevated in CA1 neurons of mid-aged and aged rats relative to young adults. The CN inhibitor, FK-506 (5 μM) completely blocked the aging-related increase in VSCC activity, reducing the activity level in aged rat neurons to that in younger rat neurons. However, aging was not associated with an increase in neuronal CN mRNA expression, nor was CN expression correlated with VSCC activity. Delivery of activated CN to primary hippocampal cultures induced an increase in neuronal L-VSCC activity but did not elevate L-VSCC protein levels. Together, the results provide the first evidence that CN activity, but not increased expression, plays a selective and necessary role in the aging-related increase in available L-VSCCs, possibly by direct activation. Thus, these studies point to altered CN function as a novel and potentially key factor in aging-dependent neuronal Ca2+ dysregulation.

Original languageEnglish
Pages (from-to)328-338
Number of pages11
JournalNeurobiology of Aging
Volume31
Issue number2
DOIs
StatePublished - Feb 2010

Bibliographical note

Funding Information:
Work supported by NIH grants AG004542 and AG010836 to P.W.L., AR046477 to S.D.K, AG020251 to N.M.P., AG024190, and AG027297 to C.M.N.

Keywords

  • Aging
  • Hippocampus
  • L-type
  • Phosphatase

ASJC Scopus subject areas

  • General Neuroscience
  • Aging
  • Clinical Neurology
  • Developmental Biology
  • Geriatrics and Gerontology

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