Transgenic mice lacking NMDAR-dependent LTD exhibit deficits in behavioral flexibility

Area of Science:

• Neuroscience
• Molecular Biology
• Behavioral Science

Background:

• Long-term potentiation (LTP) is widely studied for its role in learning and memory.
• The function of long-term depression (LTD) in cognitive processes remains less understood.
• Protein phosphatase 2A (PP2A) is a key enzyme implicated in synaptic plasticity.

Purpose of the Study:

• To investigate the role of NMDAR-dependent LTD in learning and memory.
• To determine if inhibiting PP2A affects LTD and subsequent cognitive functions.
• To explore the necessity of LTD for behavioral flexibility.

Main Methods:

• Generated transgenic mice expressing SV40 small t antigen to inhibit PP2A.
• Assessed NMDAR-dependent LTD at Schaffer collateral synapses.
• Evaluated behavioral flexibility using the Morris water maze and a delayed nonmatch to place T-maze task.

Main Results:

• Small t antigen expression successfully blocked stimulus-induced and chemically induced NMDAR-dependent LTD.
• Synaptic potentiation, depotentiation, and mGluR-dependent LTD remained unaffected.
• Mice exhibited significant deficits in behavioral flexibility in both maze tasks.

Conclusions:

• NMDAR-dependent LTD is essential for behavioral flexibility.
• Inhibition of PP2A disrupts NMDAR-dependent LTD, leading to cognitive deficits.
• LTD may facilitate learning by weakening irrelevant memory traces during new information acquisition.