mGluR-dependent persistent firing in entorhinal cortex layer III neurons

Area of Science:

• Neuroscience
• Cellular Electrophysiology
• Receptor Pharmacology

Background:

• Persistent firing in neurons is essential for memory, particularly working memory.
• Metabotropic glutamate receptors (mGluRs) are implicated in neuronal persistent firing.
• The specific role of mGluRs in entorhinal cortex (EC) persistent firing remains unclear.

Purpose of the Study:

• To investigate if entorhinal cortex (EC) layer III neurons exhibit persistent firing mediated by mGluR activation.
• To determine if this persistent firing is independent of cholinergic activation.
• To elucidate the role of group I mGluRs in EC layer III neuronal activity.

Main Methods:

• Whole-cell patch-clamp recordings were performed on rat EC slice preparations.
• Neuronal activity was stimulated via the angular bundle.
• Pharmacological agents, including cholinergic antagonists, ionotropic receptor blockers, and group I mGluR modulators, were used.

Main Results:

• Stimulation induced persistent firing in 90% of EC layer III neurons, lasting over 4.5 minutes at 2.1 Hz.
• This firing persisted in the presence of atropine and ionotropic glutamate/GABA blockers.
• Group I mGluR blockers (LY367385, MPEP) abolished persistent firing, while an agonist (DHPG) enhanced it.

Conclusions:

• Group I mGluRs play a critical role in driving persistent firing in EC layer III neurons.
• Persistent firing can be mediated by glutamatergic input alone, independent of cholinergic pathways.
• This finding highlights a key mechanism for information storage in the entorhinal cortex.