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Substance P-immunoreactive elements in laminae I and II of the chicken spinal cord: a light- and electron-microscopic
1Department of Anatomy, Yamanashi Medical College, Japan.
Insights
Substance P (SP) nerve fibers in chicken spinal cord laminae I and II were examined. SP-containing primary afferents are presynaptically modulated by distinct neurotransmitter systems.
Area of Science:
- Neuroscience
- Cell Biology
- Immunohistochemistry
Background:
- Substance P (SP) is a neuropeptide involved in pain and sensory transmission.
- Understanding SP's role in the spinal cord is crucial for pain research.
Purpose of the Study:
- To investigate the distribution and ultrastructure of Substance P-immunoreactive (SP-IR) elements in chicken spinal cord laminae I and II.
- To elucidate the synaptic relationships of SP-IR boutons.
Main Methods:
- Light and electron microscopy using an anti-SP monoclonal antibody and the indirect antibody peroxidase-antiperoxidase technique.
- Immunohistochemical analysis of SP-IR elements in the dorsal horn of the chicken spinal cord.
Main Results:
- SP-IR elements were concentrated in the dorsolateral portion of laminae I and II.
- Electron microscopy revealed two types of SP-IR boutons: large central terminals in synaptic glomeruli and small boutons.
- SP-IR boutons formed axo-axonic synapses with presynaptic profiles containing clear or dense-cored vesicles.
Conclusions:
- SP-containing primary afferents in the chicken spinal cord receive presynaptic modulation.
- Two distinct neurotransmitter or modulator systems appear to regulate SP-containing afferents.
Abstract:
Substance P (SP)-immunoreactive (IR) elements were studied in laminae I and II of the chicken spinal cord in conjunction with an anti-SP monoclonal antibody at light- and electron-microscopic levels by means of the indirect antibody peroxidase-antiperoxidase technique. At the light-microscopic level, SP-IR elements were most intensely observed in the dorsolateral portion of the dorsal horn, laminae I and II. Electron-microscopically, SP-IR boutons contained large spherical dense-cored vesicles (diameter range: 60-125 nm) and spherical clear vesicles. They were subdivided into two groups: large SP-IR boutons, which were the central terminals in synaptic glomeruli, and small SP-IR boutons. In the synaptic glomerulus, two kinds of non-IR presynaptic profiles made axo-axonic synapses with the SP-IR central terminal: one was the presynaptic profile containing pleomorphic clear vesicles and the other was the presynaptic profile containing large dense-cored vesicles. A 'septate junction'-like structure was observed between large SP-IR boutons in synaptic glomeruli. The present results suggest that SP-containing primary afferents are modulated presynaptically by two different neurotransmitter or modulator systems.
