  The lateral diffusion and trapping of neurotransmitter receptors within the
postsynaptic membrane of a neuron plays a key role in determining synaptic
strength and plasticity. Trapping is mediated by the reversible binding of
receptors to scaffolding proteins (slots) within a synapse. In this paper we
introduce a new method for analyzing the transient dynamics of synapses in a
diffusion-trapping model of receptor trafficking. Given a population of
spatially distributed synapses, each of which has a fixed number of slots, we
calculate the rate of relaxation to the steady-state distribution of bound
slots (synaptic weights) in terms of a set of local accumulation times.
Assuming that the rates of exocytosis and endocytosis are sufficiently slow, we
show that the steady-state synaptic weights are independent of each other
(purely local). On the other hand, the local accumulation time of a given
synapse depends on the number of slots and the spatial location of all the
synapses, indicating a form of transient heterosynaptic plasticity. This
suggests that local accumulation time measurements could provide useful
information regarding the distribution of synaptic weights within a dendrite.
