Miniature synaptic events maintain dendritic spines via AMPA receptor activation

We investigated the influence of synaptically released glutamate on postsyn aptic structure by comparing the effects of deafferentation, receptor antag onists and blockers of glutamate release in hippocampal Slice cultures. CA1 pyramidal cell spine density and length decreased after transection of Sch affer collaterals and after application of AMPA receptor antagonists or bot ulinum toxin to unlesioned cultures. Loss of spines induced by lesion or by botulinum toxin was prevented by simultaneous AMPA application. Tetrodotox in did not affect spine density. Synaptically released glutamate thus exert s a trophic effect on spines by acting at AMPA receptors. We conclude that AMPA receptor activation by spontaneous vesicular glutamate release is suff icient to maintain dendritic spines.