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Enhanced Long-Term Potentiation During Aging Is Masked by Processes Involving Intracellular Calcium Stores

Enhanced Long-Term Potentiation During Aging Is Masked by Processes Involving Intracellular... The contribution of Ca 2+ release from intracellular Ca 2+ stores (ICS) for regulation of synaptic plasticity thresholds during aging was investigated in hippocampal slices of old (22–24 mo) and young adult (5–8 mo) male Fischer 344 rats. Inhibition of Ca 2+ -induced Ca 2+ release by thapsigargin, cyclopiazonic acid (CPA), or ryanodine during pattern stimulation near the threshold for synaptic modification (5 Hz, 900 pulses) selectively induced long-term potentiation (LTP) to CA1 Schaffer collateral synapses of old rats. Increased synaptic strength was specific to test pathways and blocked by AP-5. Intracellular recordings demonstrated that ICS plays a role in the augmentation of the afterhyperpolarization (AHP) in old rats. The decrease in the AHP by ICS inhibition was reversed by the L-channel agonist, Bay K8644. Under conditions of ICS inhibition and a Bay K8644–mediated enhancement of the AHP, pattern stimulation failed to induce LTP, consistent with the idea that the AHP amplitude shapes the threshold for LTP induction. Finally, ICS inhibition was associated with an increase in the N -methyl- D -aspartate (NMDA) receptor component of synaptic transmission in old animals. This increase in the synaptic response was blocked by the calcineurin inhibitor FK506. The results reveal an age-related increase in susceptibility to LTP-induction that is normally inhibited by ICS and suggest that the age-related shift in Ca 2+ regulation and Ca 2+ -dependent synaptic plasticity is coupled to changes in cell excitability and NMDA receptor function through ICS. Address for reprint requests and other correspondence: T. C. Foster, Dept. of Neuroscience, McKnight Brain Institute, Univ. of Florida, PO Box 100244, Gainesville, FL 32610–0244 (E-mail: [email protected] ). http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Neurophysiology The American Physiological Society

Enhanced Long-Term Potentiation During Aging Is Masked by Processes Involving Intracellular Calcium Stores

Kumar, Ashok; Foster, Thomas C.
Journal of Neurophysiology , Volume 91 (6): 2437 – Jun 1, 2004
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References (88)

Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0022-3077
eISSN
1522-1598
DOI
10.1152/jn.01148.2003
pmid
14762159
Publisher site
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Abstract

The contribution of Ca 2+ release from intracellular Ca 2+ stores (ICS) for regulation of synaptic plasticity thresholds during aging was investigated in hippocampal slices of old (22–24 mo) and young adult (5–8 mo) male Fischer 344 rats. Inhibition of Ca 2+ -induced Ca 2+ release by thapsigargin, cyclopiazonic acid (CPA), or ryanodine during pattern stimulation near the threshold for synaptic modification (5 Hz, 900 pulses) selectively induced long-term potentiation (LTP) to CA1 Schaffer collateral synapses of old rats. Increased synaptic strength was specific to test pathways and blocked by AP-5. Intracellular recordings demonstrated that ICS plays a role in the augmentation of the afterhyperpolarization (AHP) in old rats. The decrease in the AHP by ICS inhibition was reversed by the L-channel agonist, Bay K8644. Under conditions of ICS inhibition and a Bay K8644–mediated enhancement of the AHP, pattern stimulation failed to induce LTP, consistent with the idea that the AHP amplitude shapes the threshold for LTP induction. Finally, ICS inhibition was associated with an increase in the N -methyl- D -aspartate (NMDA) receptor component of synaptic transmission in old animals. This increase in the synaptic response was blocked by the calcineurin inhibitor FK506. The results reveal an age-related increase in susceptibility to LTP-induction that is normally inhibited by ICS and suggest that the age-related shift in Ca 2+ regulation and Ca 2+ -dependent synaptic plasticity is coupled to changes in cell excitability and NMDA receptor function through ICS. Address for reprint requests and other correspondence: T. C. Foster, Dept. of Neuroscience, McKnight Brain Institute, Univ. of Florida, PO Box 100244, Gainesville, FL 32610–0244 (E-mail: [email protected] ).

Journal

Journal of Neurophysiology – The American Physiological Society

Published: Jun 1, 2004

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