A, Original traces show the effect of L-AP4 on the firing activity of labeled PVN neurons in one WKY rat and one SHR. The membrane potential value was shown on the left. B and C, Mean data (B) and percentage changes (C) show the concentration-dependent effect of L-AP4 on the firing activity of labeled PVN neurons in WKY rats (n = 15 neurons from 4 rats) and SHRs (n = 22 neurons from 6 rats). The firing rate was normalized to the respective baseline in each group. D, Mean data show the effect of repeated bath application of 50 μM L-AP4 on the firing rate of 9 labeled PVN neurons from 4 rats in WKY rats. E, Summary data show that CPPG blocked the effect of L-AP4 on the firing rate of labeled PVN neurons in WKY rats (D, n = 9 neurons from 4 rats) and SHRs (E; inhibition, n = 10 neurons; excitation, n = 7 neurons from 5 rats). Data are presented as mean ± SEM. *P < 0.05, compared with the baseline for the group. #P < 0.05, compared with the baseline in WKY rats.