The magnitude of TBS-induced long-term potentiation is significantly reduced in ArcKR mice
Although the expression of Arc protein plays an important role in mGluR-mediated LTD (Wall et al. , 2018), the involvement of Arc in potentiation: (long term (LTP) and short term (STP)) is more contentious. Previous studies have shown a role for Arc in LTP, particularly in the dentate gyrus (see introduction). In contrast, (Kyrke-Smithet al. , 2021) showed that LTP at SC-CA1 synapses was unaffected by an inducible deletion of Arc. To further investigate the role of Arc in potentiation at SC-CA1 synapses we have compared potentiation induced in ArcKR Vs. WT mice. Since Arc protein expression is enhanced and longer lasting in ArcKR mice (Wallet al. , 2018), any effects of Arc on LTP might be expected to be increased in ArcKR mice. Potentiation was evoked using theta burst stimulation (TBS, 4 bursts as in (Kyrke-Smith et al. , 2021). Following induction, there was no significant difference in the amplitude of STP between the genotypes (measured 2-3 minutes after induction, Fig 2A, B). However, LTP measured 2 hours after induction was significantly reduced in ArcKR mice (Fig 2A, C). This was not a consequence of a difference in synaptic activation, as there was no significant difference in the mean slope of baseline fEPSPs between ArcKR and WT mice (p = 0.409, Z = 0.825, U = 108, Mann Whitney).