Basal synaptic transmission in the hippocampus of ArcKR mice is
not significantly different compared to WT mice but PP-LFS mediated LTD
is significantly enhanced.
Before examining synaptic plasticity, we confirmed our previous
observations (in 21–35-day old mice, Wall et al 2018) that basal
synaptic transmission in the hippocampus of ArcKR mice is not
significantly different from that in wildtype mice (at 2-3 months of
age). There was no significant difference in the stimulus input/output
relationships (Figure 1A) or in the degree of paired-pulse facilitation
at Schaffer collateral-CA1 (SC-CA1) synapses between ArcKR and WT mice
(Figure 1B). In corroboration of these findings, there was no
significant difference in the expression of Arc protein in hippocampal
lysates obtained from WT and ArcKR mice (at 2-3 months of age, Figure
1C). We have previously shown that mGluR-mediated long-term depression
(LTD) induced with the group 1 (G1)-mGluR agonist DHPG is enhanced in
the hippocampus obtained from juvenile ArcKR mice
(Wall et al. , 2018). We
investigated whether a similar enhancement can be observed in
synaptically-induced LTD in 2–3-month-old mice (PP-LFS, Figure 1D-E).
LTD was induced by 900-paired-pulses (50 ms interval) at 1 Hz
(Oliet et al. , 1997) in the
presence of L689,560 to block NMDA receptors. The degree of depression
was significantly enhanced in slices from ArcKR mice (Figure 1D-E)
consistent with previous findings using the G1-mGluR agonist DHPG to
induce LTD (Wall et al. , 2018).