FIGURE 2.

Activation of ERK MAPK is associated with the presence of the CDC25 domain of GRF2 and is necessary but not sufficient to promote TBS-LTP by GRF proteins. A, hippocampal brain slices from WT mice (WT), DBKO mice expressing GRF2, or the chimeric GRF proteins indicated and DBKO mice (DBKO), were exposed to TBS (140 μA) and then 5 min later samples were frozen and immunostained with anti-p-ERK MAPK antibodies. Representative p-ERK MAPK signals from slices are shown (top) (*, shows approximate stimulating electrode position; ▾, shows background area chosen at least 200 μm from electrode where GRF proteins are expressed, but stimulated cells are not observed). B, representative images of stimulated brain slices stained with GRF antibodies. C, quantification of fluorescence intensity in A and B. The left bar graph represents the signals obtained from samples described in A. The signal represents that from the stimulated area minus the signal from the neighboring unstimulated area both of which express exogenous GRF proteins. This value was then compared with that obtained with brain slices from WT mice expressing endogenous GRF2. The final results are expressed as fold-change compared with WT. The right bar graph represents the signals obtained from the GRF immunostaining. All data are the average ± S.E. of at least 3 independent experiments; **, p ≤ .01; n.s., not statistically different. Scale bar, 50 μm.