Non-synaptic dendritic spines in neocortex.
A long-held assumption states that each dendritic spine in the cerebral cortex forms a synapse, although this issue has not been systematically investigated. We performed complete ultrastructural reconstructions of a large (n=144) population of identified spines in adult mouse neocortex finding that only 3.6% of the spines clearly lacked synapses. Nonsynaptic spines were small and had no clear head, resembling dendritic filopodia, and could represent a source of new synaptic connections in the adult cerebral cortex.
Arellano
J I
JI
Departamento de Neuroanatomia y Biologia Celular, Instituto Cajal (CSIC), Ave. Dr. Arce, 37, 28002 Madrid, Spain.
Espinosa
A
A
Fairén
A
A
Yuste
R
R
DeFelipe
J
J
D000818:Animals; D048430:Cell Shape / Q000502:physiology; D049229:Dendritic Spines / Q000502:physiology / Q000648:ultrastructure*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D046529:Microscopy, Electron, Transmission; D019579:Neocortex / Q000502:physiology / Q000648:ultrastructure*; D009434:Neural Pathways / Q000502:physiology / Q000648:ultrastructure*; D009473:Neuronal Plasticity / Q000502:physiology*; D011554:Pseudopodia / Q000502:physiology / Q000648:ultrastructure; D017966:Pyramidal Cells / Q000502:physiology / Q000648:ultrastructure*; D016622:Silver Staining / Q000379:methods; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure*