Ultrastructural identification of neurotransmitters

Area of Science:

• Neuroscience
• Cell Biology
• Gastroenterology

Background:

• Early 1970s research established simplistic correlations between intra-axonal vesicle types and neurotransmitters in cholinergic, adrenergic, and non-adrenergic, non-cholinergic nerves.
• The enteric nervous system (ENS) is now known to involve a complex interplay of signaling molecules.

Purpose of the Study:

• To highlight the oversimplification of early models of neurotransmitter-vesicle relationships in peripheral nerves.
• To underscore the complexity of neurotransmission within the enteric nervous system.
• To identify the need for advanced methodologies to accurately characterize ENS signaling.

Main Methods:

• Review of historical correlations between vesicle types and neurotransmitters.
• Discussion of current proposals for multiple putative transmitters in the ENS.
• Consideration of co-existence of transmitters within single nerve terminals.

Main Results:

• Established correlations between vesicle types and transmitters from the 1970s are deemed inadequate.
• The ENS likely utilizes over 16 putative transmitters.
• The co-existence of multiple transmitters within single nerve terminals significantly complicates ENS signaling.

Conclusions:

• Resolving the complexities of ENS neurotransmission requires moving beyond simplistic models.
• Advanced preparative procedures are necessary to obtain high-quality electron micrographs.
• Specific cytochemical reactions for putative transmitters and associated enzymes are crucial for accurate identification and resolution of ENS signaling pathways.