Cholinergic neurons excite cortically projecting basal forebrain GABAergic neurons

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Systems Neuroscience

Background:

• The basal forebrain (BF) is crucial for cortical activation and attention.
• BF dysfunction is implicated in neurological disorders like Alzheimer's disease.
• Understanding BF neuronal modulation is key to treating these conditions.

Purpose of the Study:

• To investigate the interaction between cholinergic neurons and cortically projecting GABAergic neurons in the basal forebrain.
• To elucidate the role of this interaction in regulating cortical activation.

Main Methods:

• Immunohistochemistry in GAD67-GFP knock-in and PV-tdTomato mice.
• Whole-cell recordings in vitro from basal forebrain slices.
• Pharmacological activation of cholinergic receptors (carbachol) and optogenetic stimulation.
• Ion substitution and reversal potential measurements.

Main Results:

• Cholinergic fibers were found to be apposed to cortically projecting GABAergic neurons containing parvalbumin (PV).
• Activation of cholinergic receptors increased the firing rate of large BF GABAergic/PV neurons.
• This excitation was mediated by sodium-permeable cation channels via M1 and M3 muscarinic receptors.
• Optogenetic stimulation of cholinergic neurons induced a sensitive inward current in GABAergic neurons.

Conclusions:

• Cortically projecting BF GABAergic/PV neurons are excited by cholinergic inputs.
• Loss of BF cholinergic neurons in Alzheimer's disease may lead to impaired cortical activation via disfacilitation of these GABAergic neurons.