Layer Variations of Long-Term Depression in Rat Visual Cortex

In vitro long-term depression (LTD) is thought to be a model for the loss of cortical responsiveness to an eye deprived of vision during the critical period. Using whole cell recording, the present study investigates the mechanisms of LTD in vitro across layers in developing rat visual cortex. LTD was induced in layers II/III, V, and VI but not layer IV with 10-min 1-Hz stimulation paired with postsynaptic depolarization. LTD in layers II/III and V could be blocked by the N-methyl-d-aspartate (NMDA) receptor antagonist d-aminophosphonovaleric acid (d-AP5) but not by 100 μM (2S)-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495), a metabotropic glutamate receptor inhibitor. In contrast, LTD in layer VI was blocked by 100 μM LY341495 and (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) but not d-AP5 and partially blocked by application of guanosine 5′-O-(2-thiodiphosphate) thilothium salt (GDP-β-S) in patch pipette, suggesting an involvement of postsynaptic group I metabotropic...