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Carbachol-induced network oscillations in an in vitro limbic system brain slice
Maxime Lévesque1, Mauro Cataldi2, Li-Yuan Chen1
1Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montréal, PQ H3A 2B4, Canada.
Neuroscience
|February 23, 2017
Summary
Carbachol induces theta oscillations in limbic brain areas. The subiculum and CA3 often drive entorhinal cortex theta generators, influenced by GABAergic signaling.
Area of Science:
- Neuroscience
- Neurophysiology
- Computational Neuroscience
Background:
- The limbic system, including the CA3, subiculum, and entorhinal cortex, plays a crucial role in cognitive functions.
- Theta frequency oscillations (5-12Hz) are prominent in these areas during various behaviors and are implicated in memory processes.
- Muscarinic receptor activation by carbachol is known to induce network oscillations in the hippocampus and related structures.
Purpose of the Study:
- To investigate the involvement of CA3, subiculum, and entorhinal cortex in carbachol-induced theta oscillations.
- To elucidate the roles of glutamatergic and GABAergic signaling in the generation and synchronization of these oscillations.
- To determine the directional flow of information and identify potential drivers of theta oscillations within these limbic structures.
Main Methods:
- Simultaneous field potential recordings from CA3, subiculum, and entorhinal cortex in an in vitro brain slice preparation.
- Pharmacological manipulation using carbachol, pirenzepine, glutamatergic receptor antagonists, and GABAA receptor blockers.
- Analysis of oscillation characteristics (frequency, duration, synchronization, latency) and the impact of pharmacological interventions.
Main Results:
- Carbachol induced synchronous theta frequency oscillations in CA3, subiculum, and entorhinal cortex.
- Oscillations were dependent on muscarinic and glutamatergic transmission but not abolished by GABAA receptor blockade.
- Entorhinal cortex oscillations often initiated later than in CA3 and subiculum, suggesting a driving role for the latter two regions.
Conclusions:
- The subiculum and CA3 regions frequently drive theta generators in the entorhinal cortex under carbachol perfusion.
- GABAA receptor signaling influences the pattern and coherence of theta oscillations but is not essential for their generation.
- These findings highlight the interconnectedness of limbic areas in generating network oscillations relevant to cognitive functions.
