Role of temporal summation in age-related long-term potentiation-induction deficits

Ephron S. Rosenzweig, Geeta Rao, Bruce L. McNaughton, Carol A. Barnes

Research output: Contribution to journalArticlepeer-review

100 Scopus citations

Abstract

Hippocampal long-term potentiation (LTP) is reduced in aged relative to young F-344 rats when peri-threshold stimulation protocols (several stimulus pulses at 100-200 Hz) are used. The present study was designed to examine the possibility that this LTP-induction deficit is caused by a reduced overlap of Schaffer-collateral inputs onto CA1 pyramidal cells (input cooperativity). This reduced input cooperativity would decrease the levels of postsynaptic depolarization during LTP induction, which might account for the age-related LTP deficit. Both behavioral data (Morris Water Maze) and electrophysiological data (intracellular recordings from hippocampal slices) were collected from adult and aged F-344 rats. To counter the effects of reduced input cooperativity, stimulus intensities were adjusted to elicit baseline excitatory postsynaptic potentials (EPSPs) of equivalent amplitude in aged and young rats. Contrary to expectations, however, an age-related LTP-induction deficit was still observed. Further evaluation of the electrophysiological data revealed that temporal summation of multiple EPSPs during high-frequency stimulation was impaired in the aged rats. Thus, despite the equalization across age groups of the baseline EPSP amplitudes, the cells of aged rats were less depolarized during the LTP-inducing stimulation than were those of young rats. This reduced total depolarization was not an artifact of the higher stimulus intensity used on aged animals, nor was it caused by a failure of aged rats' CA1 afferents to follow high-frequency stimulation. The present data therefore suggest that there is a deficit in the ability of aged rats' synapses to provide the sustained depolarization necessary to activate the LTP-induction cascade.

Original languageEnglish (US)
Pages (from-to)549-558
Number of pages10
JournalHippocampus
Volume7
Issue number5
DOIs
StatePublished - 1997

Keywords

  • Aging
  • Hippocampus
  • Learning
  • Memory
  • Slice preparation

ASJC Scopus subject areas

  • Cognitive Neuroscience

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