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Long-lasting modulation of the induction of LTD and LTP in rat hippocampal CA1 by behavioural stress and environmental enrichment

Authors

  • Alain Artola,

    1. Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
    2. Laboratory of Theoretical Neurobiology, Born-Bunge Foundation, University of Antwerp-Campus drie eiken, Universiteitsplein 1, B2610 Antwerp, Belgium
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  • Josefien C. Von Frijtag,

    1. Department of Animals, Science & Society, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
    2. Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
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  • Patrick C. J. Fermont,

    1. Department of Animals, Science & Society, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
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  • Willem Hendrik Gispen,

    1. Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
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  • Loes H. Schrama,

    1. Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
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      Sadly, since this work was done, L.H.S. has died.
  • Amer Kamal,

    1. Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
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  • Berry M. Spruijt

    1. Department of Animals, Science & Society, Utrecht University, Yalelaan 2, 3584 CM, Utrecht, The Netherlands
    2. Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
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  • *

    Sadly, since this work was done, L.H.S. has died.

Professor B.M. Spruijt, 1Department of Animals, Science & Society, as above.
E-mail: b.m.spruijt@vet.uu.nl

Abstract

Behavioural experience (e.g. chronic stress, environmental enrichment) can have long-lasting effects on cognitive functions. Because activity-dependent persistent changes in synaptic strength are believed to mediate memory processes in brain areas such as hippocampus, we tested whether behaviour has also long-lasting effects on synaptic plasticity by examining the induction of long-term potentiation (LTP) and long-term depression (LTD) in slices of hippocampal CA1 obtained from rats either 7–9 months after social defeat (behavioural stress) or 3–5 weeks after 5-week exposure to environmental enrichment. Compared with age-matched controls, defeated rats showed markedly reduced LTP. LTP was even completely impaired but LTD was enhanced in defeated and, subsequently, individually housed (during the 7–9-month period after defeat) rats. However, increasing stimulus intensity during 100-Hz stimulation resulted in significant LTP. This suggests that the threshold for LTP induction is still raised and that for LTD lowered several months after a short stressful experience. Both LTD and LTP were enhanced in environmentally enriched rats, 3–5 weeks after enrichment, as compared with age-matched controls. Because enrichment reduced paired-pulse facilitation, an increase in presynaptic release, facilitating both LTD and LTP induction, might contribute to enhanced synaptic changes. Consistently, enrichment reduced the number of 100-Hz stimuli required for inducing LTP. But enrichment may also actually enhance the range of synaptic modification. Repeated LTP and LTD induction produced larger synaptic changes in enriched than in control rats. These data reveal that exposure to very different behavioural experiences can produce long-lasting effects on the susceptibility to synaptic plasticity, involving pre- and postsynaptic processes.

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