Spine expansion and stabilization associated with long-term potentiation

Area of Science:

• Neuroscience
• Cellular Biology
• Synaptic Plasticity

Background:

• Stable synaptic plasticity is crucial for neural circuit development, learning, and memory.
• Structural remodeling of dendritic spines is linked to long-term potentiation (LTP), but their precise relationship is unclear.

Purpose of the Study:

• To investigate the relationship between structural plasticity (dendritic spine changes) and physiological plasticity (LTP).
• To determine if dendritic spine expansion and LTP are distinct or interconnected processes.

Main Methods:

• Simultaneous monitoring of excitatory postsynaptic potentials (EPSPs) and dendritic spines in CA1 pyramidal neurons.
• Utilizing combined patch-clamp recording and two-photon time-lapse imaging in acute hippocampal slices.
• Employing theta burst stimulation, NMDA receptor manipulation, protein kinase A (PKA) inhibition, protein synthesis inhibitors, and low-frequency stimulation (LFS).

Main Results:

• Theta burst stimulation induced both LTP and rapid, persistent dendritic spine expansion, both NMDA receptor-dependent.
• Spine expansion persisted even when LTP was inhibited, but became unstable without PKA or exocytosis.
• Protein synthesis inhibitors affected LTP and spine expansion similarly.
• Low-frequency stimulation reversed spine expansion via a phosphatase-dependent mechanism within a critical time window, similar to LTP reversal.

Conclusions:

• Initial expression of LTP and dendritic spine expansion are dissociable processes.
• Stabilization of structural plasticity and LTP share significant mechanistic overlap.
• NMDA receptor-dependent processes are critical for the persistent structural changes underlying synaptic plasticity.