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Sensory feedback from the urethra evokes state-dependent lower urinary tract reflexes in rat.

Publication ,  Journal Article
Danziger, ZC; Grill, WM
Published in: The Journal of physiology
August 2017

The lower urinary tract is regulated by reflexes responsible for maintaining continence and producing efficient voiding. It is unclear how sensory information from the bladder and urethra engages differential, state-dependent reflexes to either maintain continence or promote voiding. Using a new in vivo experimental approach, we quantified how sensory information from the bladder and urethra are integrated to switch reflex responses to urethral sensory feedback from maintaining continence to producing voiding. The results demonstrate how sensory information regulates state-dependent reflexes in the lower urinary tract and contribute to our understanding of the pathophysiology of urinary retention and incontinence where sensory feedback may engage these reflexes inappropriately.Lower urinary tract reflexes are mediated by peripheral afferents from the bladder (primarily in the pelvic nerve) and the urethra (in the pudendal and pelvic nerves) to maintain continence or initiate micturition. If fluid enters the urethra at low bladder volumes, reflexes relax the bladder and evoke external urethral sphincter (EUS) contraction (guarding reflex) to maintain continence. Conversely, urethral flow at high bladder volumes, excites the bladder (micturition reflex) and relaxes the EUS (augmenting reflex). We conducted measurements in a urethane-anaesthetized in vivo rat preparation to characterize systematically the reflexes evoked by fluid flow through the urethra. We used a novel preparation to manipulate sensory feedback from the bladder and urethra independently by controlling bladder volume and urethral flow. We found a distinct bladder volume threshold (74% of bladder capacity) above which flow-evoked bladder contractions were 252% larger and evoked phasic EUS activation 2.6 times as often as responses below threshold, clearly demonstrating a discrete transition between continence (guarding) and micturition (augmenting) reflexes. Below this threshold urethral flow evoked tonic EUS activity, indicative of the guarding reflex, that was proportional to the urethral flow rate. These results demonstrate the complementary roles of sensory feedback from the bladder and urethra in regulating reflexes in the lower urinary tract that depend on the state of the bladder. Understanding the neural control of functional reflexes and how they are mediated by sensory information in the bladder and urethra will open new opportunities, especially in neuromodulation, to treat pathologies of the lower urinary tract.

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Published In

The Journal of physiology

DOI

EISSN

1469-7793

ISSN

0022-3751

Publication Date

August 2017

Volume

595

Issue

16

Start / End Page

5687 / 5698

Related Subject Headings

  • Urinary Bladder
  • Urethra
  • Reflex
  • Rats, Sprague-Dawley
  • Pressure
  • Physiology
  • Muscle Contraction
  • Female
  • Feedback, Sensory
  • Animals
 

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Danziger, Z. C., & Grill, W. M. (2017). Sensory feedback from the urethra evokes state-dependent lower urinary tract reflexes in rat. The Journal of Physiology, 595(16), 5687–5698. https://doi.org/10.1113/jp274191
Danziger, Zachary C., and Warren M. Grill. “Sensory feedback from the urethra evokes state-dependent lower urinary tract reflexes in rat.The Journal of Physiology 595, no. 16 (August 2017): 5687–98. https://doi.org/10.1113/jp274191.
Danziger ZC, Grill WM. Sensory feedback from the urethra evokes state-dependent lower urinary tract reflexes in rat. The Journal of physiology. 2017 Aug;595(16):5687–98.
Danziger, Zachary C., and Warren M. Grill. “Sensory feedback from the urethra evokes state-dependent lower urinary tract reflexes in rat.The Journal of Physiology, vol. 595, no. 16, Aug. 2017, pp. 5687–98. Epmc, doi:10.1113/jp274191.
Danziger ZC, Grill WM. Sensory feedback from the urethra evokes state-dependent lower urinary tract reflexes in rat. The Journal of physiology. 2017 Aug;595(16):5687–5698.
Journal cover image

Published In

The Journal of physiology

DOI

EISSN

1469-7793

ISSN

0022-3751

Publication Date

August 2017

Volume

595

Issue

16

Start / End Page

5687 / 5698

Related Subject Headings

  • Urinary Bladder
  • Urethra
  • Reflex
  • Rats, Sprague-Dawley
  • Pressure
  • Physiology
  • Muscle Contraction
  • Female
  • Feedback, Sensory
  • Animals