Different threshold levels of postsynaptic [Ca2+]i have to be reached to induce LTP and LTD in neocortical pyramidal cells.
Changes in [Ca2+]i were measured in layer II-III pyramid cells of the rat visual cortex slices during application of either LTP or LTD inducing stimulation protocols. At dendritic sites activated by the stimulated afferents [Ca2+]i reached higher amplitudes and decayed more slowly with LTP than with LTD inducing stimuli. In the presence of Ca2+ chelators, the stimulation protocol that would normally produce LTP induced either LTD or failed to induce a synaptic modifications altogether. These results support the hypothesis that the polarity of synaptic gain changes depends on the magnitude of postsynaptic [Ca2+]i responses, the induction of LTP requiring a more pronounced surge of [Ca2+]i than the induction of LTD.
Hansel
C
C
Max-Planck-Institute for Brain Research, Frankfurt, Germany.
Artola
A
A
Singer
W
W
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D003712:Dendrites / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects; D008274:Magnesium / Q000494:pharmacology; D017072:Neostriatum / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013569:Synapses / Q000502:physiology*
D002614:Chelating Agents; D008274:Magnesium; D002118:Calcium