title: Synaptic basis for whisker deprivation-induced synaptic depression in rat somatosensory cortex.
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.
authors.affiliation: Division of Biological Sciences, University of California San Diego, La Jolla, California 92093-0357, USA. kbender@ucsd.edu
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Bender
authors.forename: Cara B
authors.initials: CB
authors.lastname: Allen
authors.forename: Vanessa A
authors.initials: VA
authors.lastname: Bender
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Feldman
mesh_terms: D000818:Animals; D016291:Dizocilpine Maleate / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D036881:Long-Term Synaptic Depression / Q000187:drug effects / Q000502:physiology*; D016202:N-Methylaspartate / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D012683:Sensory Deprivation / Q000502:physiology; D013003:Somatosensory Cortex / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014738:Vibrissae / Q000187:drug effects / Q000502:physiology*
chemical_list: D016202:N-Methylaspartate; D016291:Dizocilpine Maleate