Fig. 3.

In normal medium, LTD is expressed in slices from aged but not adult rats. A, Plot of EPSP slopes for a single adult slice bathed in normal medium (2 mmCa²⁺/2 mm Mg²⁺). LFS of Schaffer collaterals failed to depress the synaptic response, although a subsequent burst of HFS was able to instate LTP. Insetrepresents EPSP waveforms averaged at the indicated time points before and after pattern stimulation. B, Average data for slices from six aged rats and six adult rats. All slices were perfused with normal medium. LFS produced a substantial depression of aged CA3–CA1 synaptic responses (filled circles), whereas slices from adults (open circles) showed no signs of LTD. HFS reversed LTD and induced LTP in aged and adult rats, respectively. Bars represent SEM.