The accumulation of beta amyloid (A beta) can cause synaptic impairments, but the characteristics and mechanisms of the synaptic impairment induced by the accumulation of A beta in Alzheimer's disease (AD) remain unclear. In identified single neurons in a newly developed Drosophila AD model, in which A beta accumulates intraneuronally, we found an age-dependent reduction in the synaptic vesicle release probability that was associated with a decrease in the density of presynaptic calcium channel clusters and an increase in the presynaptic and postsynaptic contact length. Moreover, these alterations occurred in the absence of presynaptic bouton loss. In addition, we found that A beta expression also produced an age-dependent decrease in the amount of Bruchpilot (Brp), which plays an important role in controlling Ca2+ channel clustering and synaptic vesicle release in the presynaptic active zone. Our study indicates that the chronic accumulation of intraneuronal A beta can induce functional and structural changes in the presynaptic active zone prior to a loss of presynaptic buttons in the same neuron. (C) 2012 Elsevier Inc. All rights reserved.