Histological and electrical properties of rat dorsal root ganglion neurons innervating the lower urinary tract.
We investigated whether primary afferent neurons innervating different regions of the lower urinary tract have different histochemical and electrophysiological properties. Neurons in rat L6-S1 DRG were identified by axonal transport of a fluorescent dye. Neurofilament-negative C-fiber cells comprise approximately 70% of bladder and proximal urethral afferent neurons that send axons through the pelvic nerves, but comprise a smaller proportion (51%) of distal urethral neurons that send axons through the pudendal nerves. Isolectin-B4 (IB4) binding was detected in a higher percentage (49%) of C-fiber neurons innervating the distal urethra than in those innervating the bladder or proximal urethra (18-22%). Neurofilament-positive A-fiber neurons innervating the distal urethra had a larger average somal size than neurons innervating the bladder or proximal urethra. In patch-clamp recordings, the majority (70%) of bladder and proximal urethral neurons were sensitive to capsaicin and exhibited TTX-resistant, high-threshold action potentials, whereas a smaller proportion (53%) of distal urethral neurons exhibited TTX-resistant spikes. T-type Ca2+ currents were observed in 47% of distal urethral neurons with TTX-sensitive spikes, but not in TTX-sensitive bladder or proximal urethral neurons. In summary, afferent neurons innervating bladder or proximal urethra differ from those innervating distal urethra. The latter, which more closely resemble cutaneous afferent neurons, consist of a smaller number of C-fiber neurons containing a higher percentage of IB4-positive cells and a more diverse population of A-fiber neurons, some of which exhibit T-type Ca2+ channels. These differences may be related to different functions of respective target organs in the lower urinary tract.
Yoshimura
Naoki
N
Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. nyos@pitt.edu
Seki
Satoshi
S
Erickson
Kristin A
KA
Erickson
Vickie L
VL
Hancellor
Michael B
MB
de Groat
William C
WC
D000578:Amidines / Q000378:metabolism; D000818:Animals; D001370:Axonal Transport / Q000187:drug effects / Q000502:physiology; D020747:Calcium Channels, T-Type / Q000378:metabolism / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism; D005727:Ganglia, Spinal / Q000737:chemistry / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D016900:Neurofilament Proteins / Q000032:analysis / Q000276:immunology; D009475:Neurons, Afferent / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D037121:Plant Lectins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013779:Tetrodotoxin / Q000494:pharmacology; D014521:Urethra / Q000737:chemistry / Q000166:cytology / Q000187:drug effects / Q000294:innervation; D001743:Urinary Bladder / Q000737:chemistry / Q000166:cytology / Q000187:drug effects / Q000294:innervation; D014551:Urinary Tract / Q000187:drug effects / Q000294:innervation*
D000578:Amidines; D020747:Calcium Channels, T-Type; D005456:Fluorescent Dyes; D016900:Neurofilament Proteins; D037121:Plant Lectins; C031455:diamidino compound 253-50; D013779:Tetrodotoxin; D002211:Capsaicin