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Aspartate-like immunoreactivity in primary afferent neurons
D J Tracey1, S De Biasi, K Phend
1Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill 27599-7090.
Neuroscience
|January 1, 1991
Summary
Amino acids like glutamate and aspartate are neurotransmitters in primary afferent neurons. This study found that many dorsal root ganglion neurons contain both glutamate and aspartate, suggesting a co-release mechanism in pain signaling.
Area of Science:
- Neuroscience
- Neurochemistry
Background:
- Amino acids, particularly glutamate, are established neurotransmitters in primary afferent neurons.
- The co-release of other neuroactive substances alongside glutamate is hypothesized but not fully elucidated.
Purpose of the Study:
- To investigate the presence of elevated aspartate levels in dorsal root ganglion (DRG) neurons alongside glutamate.
- To determine if aspartate and glutamate are localized within the same neurons and their terminals.
Main Methods:
- Immunocytochemical techniques using specific antisera against aspartate and glutamate.
- Quantitative video microscopy to analyze cell size and staining intensity.
- Pre- and post-embedding immunocytochemistry with electron microscopy for terminal localization.
Main Results:
- Approximately 30% of cervical DRG neurons exhibited aspartate immunoreactivity, predominantly in small neurons (15-30 microns).
- Elevated aspartate levels were found in the same neurons that contained elevated glutamate levels.
- Aspartate was localized in terminals within the superficial laminae of the dorsal horn, including those associated with nociceptors.
Conclusions:
- The findings support the hypothesis that aspartate, in addition to glutamate, is present in nociceptive primary afferents.
- Aspartate may be co-released with glutamate from these afferents to modulate neuronal activity in the dorsal horn, potentially playing a role in pain transmission.