The present study reports changes in synaptic function and plasticity [long-term potentiation (LTP)] in a recently developed mouse model of Alzheimer's disease (CRND8 line) harboring a double amyloid precursor protein mutation (APP(swe/ind)). In 9-week-old preplaque transgenic (Tg) mice brain slices, basal synaptic function in the hippocampal CA1 area was unchanged. Only one of three different LTP induction protocols revealed early influence of genotype on synaptic plasticity. By 20 weeks of age, there were numerous plaques in the hippocampus from Tg mice associated with more robust evidence for genotype-related effects in synaptic function. Field potential maximum slope was consistently decreased and LTP was increased, irrespective of the stimulation protocol used. In addition, there was clear evidence of increased synaptic excitability in Tg mice. Furthermore, the maximum amplitude of evoked IPSCs was decreased whereas the maximum amplitude of evoked EPSCs was increased in 20-week-old Tg mice. Collectively, these results suggest a number of APP genotype-related changes in the fine-tuning of the CA1 area circuitry, some of which are likely to contribute to the pathology-dependent effects on LTP observed in CRND8 mice.