Developmental down-regulation of LTD in cortical layer IV and its independence of modulation by inhibition.
For in vitro LTD to remain viable as a model for synaptic weakening in visual cortical plasticity, it is crucial that it display a critical period for its induction within layer IV. A complicating factor, however, is that LTD in layer IV is modulated by inhibitory postsynaptic potentials (IPSPs); postsynaptic responses characterized as containing IPSPs do not depress in response to 1 Hz afferent stimulation. By blocking IPSPs intracellularly, we find that the ability to induce LTD in layer IV neurons is restored in juvenile, but not in mature animals. This developmental down-regulation of LTD induction is specific for layer IV when compared with LTD induction in layers II/III. These data are consistent with the hypothesis that an LTD-like phenomenon is involved in critical period plasticity and is apparently independent of developmental changes in inhibitory circuitry.
Dudek
S M
SM
Neurobiology Research Center, University of Alabama at Birmingham, 35294-0021, USA.
Friedlander
M J
MJ
D000818:Animals; D002415:Cats; D015536:Down-Regulation; D006168:Guinea Pigs; D017998:Leukotriene D4 / Q000502:physiology*; D008854:Microscopy, Electron; D009473:Neuronal Plasticity / Q000502:physiology; D009474:Neurons / Q000502:physiology / Q000648:ultrastructure; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*
D017998:Leukotriene D4