Phospholipid-derived choline intermediates and acetylcholine synthesis in mouse brain synaptosomes

Area of Science:

• Neuroscience
• Biochemistry
• Cell Biology

Background:

• Acetylcholine (ACh) is a crucial neurotransmitter synthesized from choline.
• Understanding the regulation of endogenous choline supply for ACh synthesis is vital for neurological research.

Purpose of the Study:

• To investigate endogenous free choline production and acetylcholine synthesis in mouse cerebral cortical synaptosomes.
• To determine the relationship between phosphatidylcholine metabolism and choline availability for ACh synthesis.
• To assess the impact of age on these processes.

Main Methods:

• Utilized cerebral cortical synaptosomes from C57BL/6 mice.
• Measured endogenous choline production and ACh synthesis rates.
• Investigated the role of phosphatidylcholine (PhC) breakdown pathways (phospholipase A2/lysophospholipase, phospholipase C).
• Assessed the effect of hemicholinium-3 and varying exogenous free choline concentrations.

Main Results:

• Endogenous choline production was ten-fold faster than ACh synthesis.
• Water-soluble intermediates from phosphatidylcholine (glycerophosphorylcholine, phosphorylcholine) increased during incubation.
• ACh synthesis was independent of exogenous choline but inhibited by hemicholinium-3, indicating reliance on synaptosome-generated choline.
• No significant differences in choline and ACh production rates were found between adult and aged mice.

Conclusions:

• Synaptosomes effectively generate free choline from phosphatidylcholine for acetylcholine synthesis.
• The high-affinity choline uptake system plays a key role in coupling choline generation to ACh synthesis.
• Age does not appear to affect the rates of choline and ACh production in mouse cerebral cortical synaptosomes.