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.
- SourceAvailable from: Warren M Grill
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- "In persons with spinal cord injury (SCI), the spino-bulbo-spinal micturition reflex is interrupted    , but a spinal reflex mediated by pudendal afferents evokes bladder contractions after SCI in the cat     and human    . This reflex is mediated by afferents that respond to flow through the urethra  , and thus a better understanding of the mechanisms involved in this urethral flow-modulated response is important to developing more effective approaches to restore bladder emptying. "
ABSTRACT: Although sensory feedback from the urethra plays an integral role in the regulation of lower urinary tract function, little is known about the properties of flow-responsive primary afferent neurons. The purpose of this study was to characterize the activity of sacral afferents that responded to fluid flow through the urethra. Single neuron action potentials were recorded extracellularly from the S1 and S2 dorsal root ganglia in eight cats anesthetized with α-chloralose. 21 of 116 cells responded to urethral flow but not to mechanical palpation of the perineum, 22 responded to both urethral flow and palpation, and 27 responded to palpation only. 34 of the 43 flow-responsive cells exhibited a firing response to 10 ml flow boluses that could be fit using a power function: FR(t)=a×(t)(b)+c, where FR is firing rate, t is time, and a, b and c are constants. In all 34 cells the 'b' term was negative, indicating that the firing rate slowed over the time course of the urethral flow. In 16 of the 24 cells that were recorded during at least four different flow rates, a power function provided a good fit of the relationship between firing rate and flow rate: FR(flow)=k×(flow)(p)+q, where k, p and q are constants. In each of these 16 cells the 'p' term was positive, indicating that the firing rate tended to increase with increases in flow rate. These are the first data to characterize the properties of flow-responsive afferents in the cat, and reveal properties that parallel those of other afferents.Neuroscience Letters 03/2012; 516(1):34-8. DOI:10.1016/j.neulet.2012.03.045 · 2.06 Impact Factor
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- "The similarity of bladder inhibition by low frequency DNP stimulation in both cats and human subjects (see Introduction), suggests the possibility of analogous excitatory pathways also existing in persons with SCI. The identification of this DNP-mediated spinal micturition pathway will depend on the use of higher stimulation frequencies (> 20 Hz) and more selective activation of nerve fibers by utilizing minimally-invasive methods, such as intraurethral or percutaneous needle stimulation (Gustafson, et al., 2004, Yoo, et al., 2007). "
ABSTRACT: Bladder contractions evoked by pudendal nerve stimulation in both spinal intact and spinal transected cats support the possibility of restoring urinary function in persons with chronic spinal cord injury (SCI). However, electrically evoked bladder responses in persons with SCI were limited to transient contractions at relatively low pressures. This prompted the present study, which presents a detailed quantification of the responses evoked by selective stimulation of individual branches of the pudendal nerve at different stimulation frequencies. In spinal intact cats anesthetized with alpha-chloralose, selective frequency-dependent electrical activation of the sensory (2 Hz<or=f<or=50 Hz), cranial sensory (f<or=5 Hz), dorsal genital (f>or=20 Hz) and rectal perineal (f<or=10 Hz) branches of the pudendal nerve evoked sustained bladder contractions dependent on the stimulation frequency. Contractions evoked by selective electrical stimulation resulted in significant increases in voiding efficiency compared to bladder emptying by distension-evoked contractions (p(ANOVA)<0.05). Acute spinal transection abolished reflex bladder contractions evoked by low frequency stimulation of the cranial sensory or rectal perineal branches, whereas contractions evoked by high frequency stimulation of the dorsal genital branch remained intact. This study presents evidence for two distinct micturition pathways (spino-bulbo-spinal vs. spinal reflexes) activated by selective afferent pudendal nerve stimulation, the latter of which may be applied to restore bladder function in persons with SCI.Experimental Neurology 07/2008; 212(1):218-25. DOI:10.1016/j.expneurol.2008.04.010 · 4.62 Impact Factor
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- "ulation could change as a result of hyper - reflexia , bladder - sphincter dyssynergia , and bladder hypertrophy resulting from chronic spinal cord injury ( de Groat et al . 1981 ; Krenz & Weaver , 1998 ) . Despite these changes , activation of urethral afferents is able to generate bladder contractions in persons with chronic spinal cord injury ( Gustafson et al . 2004 ) ."
ABSTRACT: Activation of urethral or genital afferents of the pudendal nerve can elicit or inhibit micturition, and low frequency stimulation of the compound pudendal nerve (PN) is known to produce a continence response. The present study demonstrates that PN stimulation also can elicit a micturition-like response and that the response to PN stimulation is dependent on stimulation frequency. We measured the changes in bladder pressure and external urethral sphincter (EUS) electroneurogram (ENG) evoked by PN stimulation before and up to 16 h after spinal cord transection (SCT) in cats anaesthetized with alpha-chloralose. Low frequency (10 Hz) stimulation elicited a continence-like response, including inhibition of the bladder and activation of the EUS, but mid-frequency (33 Hz) stimulation produced a micturition-like response, including excitation of the bladder without activation of the EUS. The dependence of the response on stimulus frequency was linked to interpulse interval as the same number of pulses at 10, 33 and 100 Hz produced different responses. Stimulation of the PN at 33 Hz produced bladder contractions before and 8 h after SCT provided the bladder contained a minimum volume of fluid. Only mid-range frequency stimulation with sufficient stimulus train duration produced a reduction in EUS ENG activity before and after SCT. In addition to a continence-like response, PN stimulation can also elicit a micturition-like response, and this response is dependent on stimulation frequency, stimulus train duration, and bladder volume. The ability to control the two principal functions of the bladder by pudendal nerve stimulation is an exciting prospect for neurorehabilitation.The Journal of Physiology 12/2006; 577(Pt 1):115-26. DOI:10.1113/jphysiol.2006.111815 · 4.54 Impact Factor