Fig. 1.

R,S-Dihydroxyphenylglycine (DHPG) application facilitates subsequently induced long-term synaptic potentiation (LTP). Field excitatory postsynaptic potentials (fEPSPs) were recorded from the CA1 region of hippocampal slices from either (A) wildtype (WT) or (B) Fmr1 knockout mice (KO). After 1 h of baseline recording, unprimed slices were administered a 1-s 100-Hz tetanus (indicated by arrow), which induced a modest level of LTP in both WT and KO slices (WT: 111.2 ± 2.1%, n = 9 slices from 9 animals, open black circles; KO: 113.8 ± 3.1%, n = 9 slices from 8 animals, open gray circles). In both genotypes, a 10-min priming application of the group 1 metabotropic glutamate receptor (Gp1 mGluR) agonist DHPG (10 μM, black bar) significantly enhanced the magnitude of subsequent LTP induced using this same 100-Hz tetanus (WT: 123.9 ± 3.8%, n = 11 slices from 11 animals, closed black circles, P < 0.02; KO: 133.7 ± 6.7%, n = 11 slices from 10 animals, closed gray circles, P < 0.02). Representative field potential traces (average of 10 sweeps) were taken at times indicated by numerals.