Alterations of synaptic turnover rate in aging may trigger senile plaque formation and neurodegeneration

Carlo Bertoni-Freddari, Patrizia Fattoretti, Belinda Giorgetti, Yessica Grossi, Marta Balietti, Tiziana Casoli, Giuseppina Di Stefano, Gemma Perretta

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The changes of synaptic ultrastructure were investigated by morphometry in the frontal (FC) and temporal (TC) cortex of adult and aged monkeys, to assess the potential role of age-related synaptic deterioration in neurodegeneration. The average synaptic size (S), the synaptic numeric density (Nv: number of synapses/μm3 of tissue), the synaptic surface density (Sv: overall area of synaptic junctional zones/μm3 of tissue), and the number of synapses/neuron (Syn/Neur) were calculated. In FC, significant differences of Nv and Sv due to age were not revealed, while the S value was significantly increased in the aged animals. In TC, Sv did not change in relation to age, whereas Nv was significantly decreased and S significantly increased in aged monkeys. A percent distribution of S showed that the fraction of enlarged synapses (>0.20 μm2) was higher in TC than in FC, regardless of the age of the animals (21.3% versus 16.9% in adult and 33.9% versus 26.0% in aged monkeys, respectively). In aged animals, Syn/Neur was not significantly decreased in TC and not significantly increased in FC (4.4%). The above morphometric parameters account for the ongoing rearrangements of synaptic ultrastructure, reacting to the environmental stimuli. Our findings provide evidence of an age-related decline of synaptic plasticity in the brain of aged monkeys that is statistically significant in TC. According to current literature data on synaptic structural dynamics, this decay may represent an early and subtle alteration able to trigger the development of senile plaques and neurodegenerative events.

Original languageEnglish
Title of host publicationAnnals of the New York Academy of Sciences
Number of pages10
Publication statusPublished - Jan 2007

Publication series

NameAnnals of the New York Academy of Sciences
ISSN (Print)00778923
ISSN (Electronic)17496632


  • Alzheimer's disease
  • E-PTA staining
  • Macaca fascicularis
  • Senile plaques
  • Synaptic morphometry
  • Synaptic numeric density
  • Synaptic pathology
  • Synaptic perforations
  • Synaptic plasticity
  • Synaptic size

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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