The brain's record of experience: kindling-induced enlargement of the active zone in hippocampal perforated synapses.

Kindling is a consequence of intermittent electrical stimulation of a local forebrain area leading to a durable augmentation of synaptic responsiveness in the stimulated circuit. The basis for this functional change is unknown, but there is evidence suggesting that it entails a structural modification of synapses. The present report demonstrates that hippocampal kindling induces a selective enlargement of active zones in perforated axospinous synapses formed by stimulated axons. Since the active zone is the site of intracellular transmission, its enlargement involving only a certain subpopulation of synapses provides a likely structural substrate of synaptic plasticity associated with kindling.