Synaptically released acetylcholine evokes Ca2+ elevations in astrocytes in hippocampal slices

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Astrocyte Biology

Background:

• Bidirectional communication between glial cells and neurons is increasingly recognized.
• Astrocytes, a type of glial cell, play crucial roles in brain function.
• Cholinergic signaling is vital for various cognitive processes.

Purpose of the Study:

• To investigate whether rat hippocampal astrocytes respond to synaptically released acetylcholine.
• To elucidate the mechanisms underlying astrocyte responses to cholinergic input.

Main Methods:

• Whole-cell recordings of membrane currents and intracellular calcium levels in hippocampal astrocytes.
• Stimulation of cholinergic afferents in brain slices.
• Application of pharmacological agents including tetrodotoxin, Cd2+, 4-aminopyridine, glutamate transporter antagonists, and atropine.

Main Results:

• Synaptic stimulation evoked long-lasting inward currents and increased intracellular calcium in astrocytes.
• These responses were dependent on synaptically released neurotransmitters and involved electrogenic glutamate transporter activity.
• Calcium elevations were mediated by muscarinic cholinergic receptors and involved intracellular calcium mobilization.
• Subcellular domains within astrocytes exhibited independent calcium variations.

Conclusions:

• Rat hippocampal astrocytes are responsive to synaptically released acetylcholine.
• Cholinergic neuron-astrocyte signaling occurs via muscarinic receptors, leading to intracellular calcium release.
• Astrocytes are targets of axonal inputs, indicating a role in synaptic integration.