Urothelial bladder afferent neurons in the rat are anatomically and neurochemically distinct from non-urothelial afferents

• Published in: Brain research Vol. 1689; pp. 45 - 53
• Main Authors: Clodfelder-Miller, Buffie J., Kanda, Hirosato, Gu, Jianguo G., Creighton, Judy R., Ness, Timothy J., DeBerry, Jennifer J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.06.2018
• Subjects: Animals; Calcium - metabolism; Female; Ganglia, Spinal - cytology; Ganglia, Spinal - metabolism; Isothiocyanates - pharmacology; Lumbar Vertebrae; Membrane Potentials - drug effects; Membrane Potentials - physiology; Neuroanatomical Tract-Tracing Techniques; Neurons, Afferent - cytology; Neurons, Afferent - drug effects; Neurons, Afferent - metabolism; Patch-Clamp Techniques; Pelvic nerve; Peripheral Nervous System Agents - pharmacology; Primary afferent neuron; Random Allocation; Rats, Sprague-Dawley; Sacrum; TRPA1; TRPA1 Cation Channel - agonists; TRPA1 Cation Channel - metabolism; Urinary bladder; Urinary Bladder - innervation; Urothelium; Urothelium - innervation; Pelvic nerve; Urinary bladder; TRPA1; Primary afferent neuron; Urothelium
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2017.12.023

•Urothelium-innervating sensory afferent neurons were identified in the rat.•Urothelial afferents comprised 14.4% of urinary bladder L6-S1 DRG neurons.•Non-urothelial afferents comprised 85% of bladder-innervating L6-S1 neurons.•Afferent populations did not differ in their electrophysiological parameters.•Fewer urothelial than non-urothelial afferents expressed functional TRPA1. There is mounting evidence underscoring a role for the urothelium in urinary bladder sensation. Previous functional studies have identified bladder primary afferents with mechanosensitive properties suggesting urothelial innervation and/or communication. The current study identifies a group of urothelium-innervating afferent neurons in rat, and characterizes and compares the properties of these and non-urothelial afferent neuron populations. Lumbosacral (LS) primary afferent neurons were retrogradely labeled using intraparenchymal (IPar) microinjection or intravesical (IVes) infusion of tracer into the bladder. Using these techniques, separate populations of neurons were differentiated by dorsal root ganglion (DRG) somata labeling and dye distribution within the bladder. IPar- and IVes-labeled neurons accounted for 85.0% and 14.4% of labeled L6-S1 neurons (P < .001), respectively, with only 0.6% of neurons labeled by both techniques. Following IVes labeling, dye was contained only within the periurothelial bladder region in contrast to non-urothelial distribution of dye after IPar labeling. Electrophysiological characterization by in situ patch-clamp recordings from whole-mount DRG preparations indicated no significant difference in passive or active membrane properties of IPar and IVes DRG neurons. However, calcium imaging of isolated neurons indicates that a greater proportion of IPar- than IVes-labeled neurons express functional TRPA1 (45.7% versus 25.6%, respectively; P < .05). This study demonstrates that two anatomically distinct groups of LS bladder afferents can be identified in rat. Further studies of urothelial afferents and the phenotypic differences between non-/urothelial afferents may have important implications for normal and pathophysiological bladder sensory processing.