Year: 2004
Type: conference-abstract
Abstract: INTRODUCTION AND OBJECTIVE:The urethra has both proximal smooth muscle and mid urethral striated muscle (MUSM)components with different innervations and neurotransmitters.Which sphincter is more important to guard against stress urinary incontinence (SUI)?We provide data that separate slow tonic and quick phasic components of the urethral continence reflexes.METHODS: In female rats, urethral contractile responses and leak point pressure (LPP)were measured during passive increments in intravesical pressure (Pves) (20-60 cmH20) to evaluate the bladder-to-urethral continence reflexes during Valsalva-like passive Pves elevation.The sneeze reflex was induced by rat whisker into the nostrils under anesthesia to evaluate the sneeze-urethral continence reflex.The effects of bilateral transection of either pelvic nerves (PN), pudendal nerves (PuN), nerves to ilio/pubococcygeous muscles (IPMN) or hypogastric nerves (HGN) on urethral response were examined.RESULTS: During Pves elevation, a portion of the middle to proximal urethra (12.5-15 rom from the urethral orifice) showed Pves-dependent tonic contractile responses that were abolished by cutting PN bilaterally.In PN-intact rats, bilateral transection of either HGN, PuN or IPMN reduced contractile responses.In PN-transected rats, LPP was significantly reduced 30-35% compared to normal rats whose LPP was 48.4 :!:: 0.8 em.Phasic contractile responses which did not disappear after opening the abdomen were observed at the middle urethra during sneezing.The MUSM responses were independent of the strength of sneezing.Pressure responses at the middle urethra during sneeze were negligible when somatic nerves (PuN and IPMN) were transected.In somatic nerve-transected rats, sneeze LPP was 16.2 :!:: 2.1 em, while there was no urinary leakage in normal rats during sneeze.CONCLUSIONS: The urethral continence mechanism has two components.Tonic resistance during Valsalva-like Pves elevation is mediated by the proximalto-middle smooth/striated muscles innervated by hypogastric sympathetic adrenergic nerves and somatic nerves.The additional phasic response is mediated by the MUSM innervated by somatic nerves with ACh binding nicotinic receptors.The immediate phasic urethral contraction in response to sneeze almost exclusively occurs in the mid urethra.The proximal urethra is important to maintain urethral tone but may not be quick enough to guard against sudden stress maneuvers.Drugs that can increase the striated sphincter phasic guarding reflex are more likely to be clinically successful to treat SUI.
Source: The Journal of Urology
Authors: Robert J. Stein, Brandon S. Minnery, Macrina Xavier, Soledad Santos, Yukio Hayashi, William J. Futrell, Ronald L. Hrebinko, Joel B. Nelson, Naoki Yoshimura, Michael B. Chancellor, Fernando De Miguel
Language: English
Subfield: Urology
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2793721062