Pathway-specific TNF-mediated metaplasticity in hippocampal area CA1

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Hippocampal Function

Background:

• Metaplasticity regulates synaptic plasticity direction, amplitude, and persistence.
• Previous work identified heterodendritic metaplasticity in hippocampal CA1, where stratum oriens (SO) stimulation suppressed stratum radiatum (SR) long-term potentiation (LTP).
• Tumor necrosis factor (TNF) mediated this effect in wild-type and Alzheimer's disease models.

Purpose of the Study:

• To investigate pathway specificity of priming-induced metaplasticity at CA1 pyramidal cell afferent synapses.
• To determine if LTP at other CA1 afferent pathways is affected by SO priming stimulation.
• To compare the sensitivity of different CA1 afferent pathways to TNF-mediated LTP inhibition.

Main Methods:

• Electrophysiological recordings in hippocampal slices.
• High-frequency priming stimulation in different hippocampal layers (SO, SR, stratum lacunosum moleculare - SLM).
• Pharmacological application of TNF and assessment in wild-type and TNFR1 knockout mice.

Main Results:

• Priming stimulation in SO selectively inhibited LTP in SR, but not in other independent pathways within SO or in SLM.
• SR synapses demonstrated higher sensitivity to LTP inhibition by pharmacological TNF priming compared to SO or SLM.
• Metaplasticity effects were observed in both sexes and were absent in TNFR1 knockout mice, confirming TNF receptor involvement.

Conclusions:

• CA1 heterodendritic metaplasticity exhibits unexpected pathway specificity.
• Schaffer collateral/commissural synapses in SR are particularly susceptible to metaplasticity.
• This pathway specificity may represent a key regulatory mechanism for information processing and susceptibility to neuroinflammation.