Postsynaptic Signals Mediating Induction of Long-Term Synaptic Depression in the Entorhinal Cortex
Figure 3
Long-term depression is dependent
on activation of the calmodulin-dependent protein phosphatase calcineurin.
Although LTD was only partially inhibited by pre-exposure to cyclosporin A, it
was completely blocked when FK506 was included in the recording electrode
solution. (a) Pre-exposure of slices to the calcineurin inhibitor cyclosporin
A (250M) for 1.5 to 3 hours resulted in a partial block of LTD by repeated
paired-pulse stimulation. The amount of LTD induced was smaller than in control
ACSF and was close to statistical significance (). (b) Including the FK506 in the recording electrode solution to directly block
postsynaptic calcineurin prevented the induction of LTD. Analysis of group responses showed a
significant increase in responses during the baseline period, but responses in
control cells indicate that this increase is transient and unlikely to have
affected measurement of LTD. Inhibition of postsynaptic calcineurin therefore
prevents induction of LTD in layer II cells of the entorhinal cortex.
