Pressure‐volume analysis of rat's micturition cycles in vivo

• Published in: Neurourology and urodynamics Vol. 39; no. 5; pp. 1304 - 1312
• Main Authors: Peng, Hsien‐Yu, Lai, Cheng‐Yuan, Hsieh, Ming‐Chun, Ho, Yu‐Cheng, Lin, Tzer‐Bin
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.06.2020; John Wiley and Sons Inc
• Subjects: Animals; Atropine; Bladder; Ethyl carbamate; Female; micturition; Muscarine; Muscle contraction; Muscle Contraction - physiology; Original Basic Science; Pressure; pressure‐volume loop; rat; Rats; Rats, Sprague-Dawley; Rhythms; thermodynamics; Urethra; Urethra - physiology; Urinary bladder; Urinary Bladder - physiology; Urination; Urination - physiology; Urodynamics - physiology; thermodynamics; pressure-volume loop; rat; micturition; urinary bladder
• ISSN: 0733-2467; 1520-6777
• DOI: 10.1002/nau.24363

Aims Though the pressure‐volume analysis (PVA), a method based on thermodynamics, is broadly used for assaying cardiac functions, its potential application on the physiology/pathophysiology of the urinary bladder, which processes resemble thermodynamic cycles to the heart, has not been established. Methods Cystometry recording intravesical pressure (IVP) and intravesical volume (IVV) of rhythmic voiding contractions caused by a constant saline infusion (0.04 mL/min) were carried out in forty urethane‐anesthetized female Sprague‐Dawley rats, and the PVA was established by plotting IVP against IVV. Results Pressure‐volume points shaped coincident enclosed loops, and loop‐associated urodynamic parameters kept stable under a constant infusion rate (0.04 mL/min). Enhancing preload (by elevating infusion rates to 0.08 and 0.12 mL/min) increased the area enclosed by the loop (Apv) and shifted loops to the right and slightly upward. Augmenting afterload (by enhancing resistances using 1/4 and 1/2 urethra clamping) increased Apv and shifted loops markedly to the right and upward. Without affecting Apv, muscarine (0.01 and 0.1 mM)‐induced inotropic states shifted loop to the left and upward that was as opposed to the atropine (0.01 and 0.1 mM)‐induced anti‐inotropic state. Conclusions Not only consistently assayed baseline bladder functions, PVA but also validly measured modified bladder functions due to altered extrinsic environment and intrinsic contractility of the bladder itself. In accompanied by cystometry, PVA could provide a clear concept about the relationship between time, pressure, and volume in the voiding activity.