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Vasoactive intestinal polypeptide in sacral primary sensory pathways in the cat
C W Morgan1, P T Ohara, D E Scott
1Department of Pathology and Anatomy, Eastern Virginia Medical School, Norfolk 23501, USA. cwm@evms.edu
The Journal of Comparative Neurology
|May 13, 1999
Summary
Vasoactive intestinal polypeptide (VIP) fibers in the cat sacral spinal cord are unmyelinated C-fibers. These VIP terminals primarily target laminae I and V, suggesting diverse roles in bladder reflexes.
Area of Science:
- Neuroscience
- Urology
- Cell Biology
Background:
- Unmyelinated sensory axons in the sacral spinal cord are implicated in bladder reflexes.
- Vasoactive intestinal polypeptide (VIP) was previously thought to be exclusively in sensory C-fibers innervating the bladder.
Purpose of the Study:
- To describe the morphology of VIP-immunoreactive fibers in the sacral spinal cord of the cat.
- To investigate the distribution and synaptic characteristics of VIP terminals in the sacral spinal cord.
Main Methods:
- Combined light and electron microscopy.
- Immunohistochemistry for VIP.
- Analysis of VIP-immunoreactive unmyelinated axons, varicosities, and synaptic terminals.
Main Results:
- VIP immunoreactivity was found in unmyelinated axons throughout the sensory pathway, including dorsal root ganglia and Lissauer's tract.
- VIP-immunolabeled varicosities and terminals were observed in sacral spinal cord laminae I, IIo, V, VII, and X.
- VIP terminals, originating from C-fibers, exhibited diverse morphologies and synaptic connections, primarily in laminae I and V.
Conclusions:
- VIP terminals in the cat sacral spinal cord originate exclusively from C-fibers.
- The varied morphology of VIP terminals suggests heterogeneous origins and functions related to the lower urinary tract.
- VIP-containing C-fibers likely play a significant role in modulating bladder reflexes.
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