Slide 24

Depolarization of the Presynaptic Membrane Potential at the Calyx of Held Results in Large Increases in the Amplitude of Evoked EPSCs

Figure 24. The amplitude of EPSP/EPSCs evoked at the calyx of Held is strongly dependent upon the membrane potential of the presynaptic terminal.  B.  The amplitude of the postsynapic potential increases approximately 10% per mV of depolarization.  Further studies by this group demonstrated that changes in presynaptic Calcium levels may be responsible for these effects.  In our study, we found that buffering Calcium abolished the facilitatory effect of membrane potential on EPSP amplitude, suggesting that a similar mechanism may also operate in the cerebral cortex.