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Vanilloid receptor 1 expression in the rat urinary tract
1Institute of Histology and Embryology, Faculty of Medicine of Oporto, IBMC of University of Oporto, Porto, Portugal.
Neuroscience
|April 3, 2002
Summary
Sensory nerve fibers expressing the vanilloid receptor type 1 (VR1) are abundant in the rat urinary tract. These capsaicin-sensitive fibers, primarily peptide-containing, may mediate pain and control bladder muscle tone.
Area of Science:
- Neuroscience
- Urology
- Cell Biology
Background:
- Capsaicin sensitivity in sensory fibers is linked to the vanilloid receptor type 1 (VR1).
- The distribution and function of VR1-expressing fibers in the urinary tract are not fully understood.
Purpose of the Study:
- To investigate the distribution, morphology, and neurochemical content of VR1-expressing nerve fibers in the rat urinary tract.
- To examine the effect of resiniferatoxin on VR1 expression in the bladder.
Main Methods:
- Immunolabeling for VR1, substance P, and calcitonin gene-related peptide.
- Confocal and electron microscopy.
- Evaluation of isolectin B4 binding.
- Intravesical administration of resiniferatoxin.
Main Results:
- Numerous VR1-immunoreactive fibers were found throughout the rat urinary tract, excluding the kidney.
- In the bladder, most VR1 fibers co-expressed substance P or CGRP and did not bind isolectin B4.
- Electron microscopy revealed VR1 in unmyelinated axons and varicosities near epithelial and smooth muscle cells.
- Resiniferatoxin caused a transient decrease in VR1 immunoreactivity.
Conclusions:
- Primary sensory fibers expressing VR1 are abundant in the rat urinary tract and are predominantly peptide-containing.
- VR1-expressing nerve endings in the bladder mucosa likely play a role in nociception and reflex micturition control.
- The close association of VR1 fibers with smooth muscle suggests a role in regulating bladder muscle tone.