A urethral afferent mediated excitatory bladder reflex exists in humans.
ABSTRACT An excitatory reflex between urethral flow receptors and the bladder has been established in animals, but attempts to demonstrate this reflex in humans using urethral fluid flow have been inconclusive. Intraurethral electrical stimulation has recently been shown to generate bladder contractions in animals and was applied to study the presence of an excitatory urethra to bladder reflex in humans. The prostatic urethra was stimulated electrically via a catheter-based electrode in five men with complete spinal cord injury. Bladder contractions were generated in four of five individuals, however, only when the bladder volume was sufficiently large. These results demonstrate the presence of a volume dependent excitatory bladder reflex mediated by urethral afferent nerve fibers and the lumbosacral spinal cord.
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ABSTRACT: The flowing of fluid along the urethra can facilitate the bladder micturition contraction, a reflex appropriate to achieve complete bladder emptying. The response has been observed in animals studied in the decerebrate, spinal, or anesthetized intact state but is difficult to demonstrate in awake, healthy humans. The aim of this study was to investigate this reflex in the awake, intact state using urodynamics in the ewe. The animals were fully awake and lay gently restrained on a recording table. The bladder was catheterized, and urethral flows were obtained by slowly injecting saline at the level of the proximal urethra. Bladder and rectal pressure were monitored, and the responses to urethral flow were tested at various bladder volumes. Urethral flows consistently evoked detrusor contractions in all animals. The response started approximately 2 seconds after the beginning of the flow and largely outlasted the stimulus. Its amplitude was similar to that of the bladder-to-bladder micturition reflex, and, like the latter, it always required some degree of bladder filling to appear. The reflex was selectively suppressed by local anesthesia of the urethral mucosa, indicating that the effect must originate from urethral receptors. Small urethral flows thus appear to elicit large bladder micturition contractions in awake healthy animals, and the reflex could be quite significant during the normal micturition. That this reflex is found in all studied species further supports the notion that the negative results in normal awake humans are owing to descending inhibitory controls rather than to the lack of appropriate pathways.Neurourology and Urodynamics 02/2001; 20(5):641-9. · 2.67 Impact Factor
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ABSTRACT: The purpose of the present study was to determine the peripheral neural pathways, spinal distribution, sizes, and peptide transmitter content of primary afferent and autonomic efferent neurons that innervate the prostate gland. Retrograde transport of the fluorescent dye "fast blue" (injected into the prostate gland) was combined with neurotransmitter immunohistochemistry. Lesions of the pelvic and pudendal nerve were used to determine the peripheral neural pathways. The majority of the afferent innervation arose from the sacral dorsal root ganglia (DRG) and was equally comprised of small, substance P- and calcitonin gene-related peptide-immunoreactive (IR) neurons and large, non-IR neurons. The majority (70%) of the afferent axons traversed the pelvic nerve with the remainder traversing the pudendal nerve. Fewer afferent neurons were located in lumbar DRG; nearly all of these were small, peptidergic neurons. Efferent autonomic neurons were located in the inferior mesenteric ganglia (IMG), sympathetic chain ganglia (SCG), and pelvic plexus ganglia (PPG). Nearly all efferent neurons in the IMG and SCG, but only 2/3 of the PPG neurons, contained dopamine-beta-hydroxylase. Substantial neuropeptide Y innervation was derived from the SCG but not the IMG or PPG. First, clinical reports suggested that sensory innervation of the prostate would be purely nociceptive in nature (implied by small, peptide-IR neurons). However, the present study suggests that there may also be a substantial, presumably non-nociceptive, afferent innervation (implied by findings of large, non-IR neurons). Second, 3 sources of autonomic efferent innervation exist, each being different in the distribution of transmitter phenotypes. Understanding the physiological role of putative non-nociceptive primary afferent neurons, and the differential roles of the various autonomic neurons, is likely to be important in developing therapies for the treatment of prostatic diseases, such as benign prostatic hyperplasia and prostatodynia.The Journal of Urology 04/1997; 157(3):1018-24. · 3.70 Impact Factor