Synaptic basis for whisker deprivation-induced synaptic depression in rat somatosensory cortex

J Neurosci. 2006 Apr 19;26(16):4155-65. doi: 10.1523/JNEUROSCI.0175-06.2006.

Abstract

Whisker deprivation weakens excitatory layer 4 (L4) inputs to L2/3 pyramidal cells in rat primary somatosensory (S1) cortex, which is likely to contribute to whisker map plasticity. This weakening has been proposed to represent long-term depression (LTD) induced by sensory deprivation in vivo. Here, we studied the synaptic expression mechanisms for deprivation-induced weakening of L4-L2/3 inputs and assessed its similarity to LTD, which is known to be expressed presynaptically at L4-L2/3 synapses. Whisker deprivation increased the paired pulse ratio at L4-L2/3 synapses and slowed the use-dependent block of NMDA receptor currents by MK-801 [(5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate], indicating that deprivation reduced transmitter release probability at these synapses. In contrast, deprivation did not alter either miniature EPSC amplitude in L2/3 neurons or the amplitude of quantal L4-L2/3 synaptic responses measured in strontium, indicating that postsynaptic responsiveness was unchanged. In young postnatal day 12 (P12) rats, at least 4 d of deprivation were required to significantly weaken L4-L2/3 synapses. Similar weakening occurred when deprivation began at older ages (P20), when synapses are mostly mature, indicating that weakening is unlikely to represent a failure of synaptic maturation but instead represents a reduction in the strength of existing synapses. Thus, whisker deprivation weakens L4-L2/3 synapses by decreasing presynaptic function, similar to known LTD mechanisms at this synapse.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Dizocilpine Maleate / pharmacology
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology
  • Long-Term Synaptic Depression / drug effects
  • Long-Term Synaptic Depression / physiology*
  • N-Methylaspartate / pharmacology
  • Rats
  • Rats, Long-Evans
  • Sensory Deprivation / physiology
  • Somatosensory Cortex / drug effects
  • Somatosensory Cortex / physiology*
  • Synapses / drug effects
  • Synapses / physiology*
  • Time Factors
  • Vibrissae / drug effects
  • Vibrissae / physiology*

Substances

  • N-Methylaspartate
  • Dizocilpine Maleate