Silent synapses during development of thalamocortical inputs.
During development, activity-dependent mechanisms are thought to contribute to the refinement of topographical projections from the thalamus to the cortex. Because activity-dependent increases in synaptic strength may contribute to the stabilization of synaptic connections, we have explored the mechanisms of long-term potentiation (LTP) at thalamocortical synapses in rat somatosensory (barrel) cortex. During early postnatal development (postnatal days 2-5), we find that a significant proportion of thalamocortical synapses are functionally silent and that these are converted to functional synapses during LTP. Silent synapses disappear by postnatal day 8-9, the exact time at which the susceptibility of these synapses to LTP is lost. These findings suggest that the activity-dependent conversion of silent to functional synapses due to correlated pre- and postsynaptic activity may contribute to the early development and refinement of thalamocortical inputs to cortex.
Isaac
J T
JT
Department of Psychiatry, University of California, San Francisco 94143, USA.
Crair
M C
MC
Nicoll
R A
RA
Malenka
R C
RC
D000200:Action Potentials; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D017774:Long-Term Potentiation; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D051381:Rats; D013003:Somatosensory Cortex / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission; D013788:Thalamus / Q000502:physiology*