Glycinergic Input to the Mouse Basal Forebrain Cholinergic Neurons.
Zsuzsanna Bardóczi1,2, Balázs Pál3, Áron Kőszeghy3
1Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, HAS, 1083, Budapest, Hungary.
Summary
Glycine, a key inhibitory neurotransmitter, directly impacts basal forebrain cholinergic neurons. This study reveals glycine
Area of Science:
- Neuroscience
- Neurochemistry
- Cellular Biology
Background:
- The basal forebrain (BF) is crucial for cortical arousal, receiving activating inputs from the brainstem.
- Knowledge regarding inhibitory brainstem inputs to the BF, particularly their effect on cholinergic functions, is limited.
- Glycine acts as both an inhibitory neurotransmitter in the brainstem and a gliotransmitter.
Purpose of the Study:
- To investigate the interaction between glycine and basal forebrain cholinergic (BFC) neurons in male mice.
- To identify the sources and mechanisms of glycine's inhibitory action on BFC neurons.
Main Methods:
- Immunohistochemistry to localize glycine receptor α subunits and glycine transporters (GLYT1, GLYT2) in relation to choline acetyltransferase (ChAT)-expressing neurons.
- Electrophysiological recordings (whole-cell) to measure spontaneous inhibitory postsynaptic currents (sIPSCs) in BFC neurons.
- Retrograde tracing from the BF to identify brainstem origins of glycinergic projections.
- Ultrastructural analysis to examine synaptic relationships between glycinergic terminals, glial processes, and BFC neurons.
Main Results:
- Glycine receptor α subunit-immunoreactive sites were found on BFC neurons.
- Glycine application induced strychnine-sensitive sIPSCs in BFC neurons, indicating direct inhibitory effects.
- Glycine transporters (GLYT1, GLYT2) were localized around BFC neurons and their synapses, suggesting tight extracellular glycine control.
- The brainstem raphe magnus was identified as a major source of glycinergic axons projecting to the BF.
Conclusions:
- Glycine directly modulates the activity of basal forebrain cholinergic neurons.
- Glycinergic inputs from the brainstem, originating from areas like the raphe magnus, play a significant role in regulating BFC neuron function.
- The localization of glycine transporters highlights a sophisticated mechanism for controlling extracellular glycine levels in the basal forebrain.
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