Nonvoiding Activity of the Guinea Pig Bladder Bart T. Biallosterski,* Gommert A. van Koeveringe, Philip E. van Kerrebroeck, James I. Gillespie and Stefan G. de Wachter† From the Department of Urology, Maastricht University Medical Centre and European Graduate School of Neuroscience, Department of Psychiatry and Neuropsychology, Maastricht University, Maastricht, The Netherlands, and Uro-physiology Research Group, Institute of Cellular Medicine, Medical School, Newcastle University (JIG), Newcastle upon Tyne, United Kingdom Purpose: Detrusor nonvoiding contractions occur in up to 70% of healthy indi- viduals. These contractions increase in those with pathological detrusor function and may be associated with afferent activity. We examined nonvoiding contrac- tions in the urethane anesthetized guinea pig bladder and studied the effect of filling rate and intravesical volume. Materials and Methods: A total of 14 guinea pigs were anesthetized and under- went bladder catheterization at the dome. In 6 guinea pigs bladder infusion was continuous and 2 physiological filling rates were used, including 25 (0.75 HD) and 50 l per minute (1.5 HD). In another 8 guinea pigs isovolumetric cystometry was done by filling the bladder incrementally and recording at low, medium and high intravesical volume. Results: Nonvoiding contractions were apparent in all animals. Contractions increased in frequency and amplitude as the bladder filled. Different phases were identified. Immediately after a void no nonvoiding contractions were observed, followed by continuous activity, first with small contractions, and later with small and large contractions. Small nonvoiding contractions showed a phasic pattern in frequency while the frequency of large nonvoiding contractions slowly increased or remained stable. The frequency and amplitude of nonvoiding contractions were higher at a faster filling rate and a higher intravesical volume. Conclusions: Nonvoiding contractions are present in the anesthetized guinea pig. Under normal physiological conditions they increase in amplitude and fre- quency with the increase in the filling rate and in intravesical volume. Small and large nonvoiding contractions differ in frequency pattern and occur at different bladder filling periods. This may illustrate different afferents functioning during bladder filling, which could be important for understanding bladder pathology. Key Words: urinary bladder, muscle contraction, afferent pathways, urination disorders, guinea pigs Abbreviations and Acronyms NVC = nonvoiding contraction Submitted for publication October 6, 2010. Study received Maastricht University local ethical committee approval. Supported by the WAMU Foundation and a BJU collaborative research grant. * Correspondence: Urology Department, Maas- tricht University Medical Centre, Post Office Box 5800, 6202 AZ Maastricht, The Netherlands (tele- phone: + 31 43 3872722; FAX: + 31 43 3875259; e-mail: biallosterski@hotmail.com). † Financial interest and/or other relationship with Medtronic. FOR decades the bladder was believed to be silent, ie without any transient pressure increases during the filling phase, and detrusor overactivity was considered pathological. These involuntary detrusor contractions may lead to symptoms such as ur- gency, increased frequency of voiding and incontinence, which seriously af- fect quality of life and the ability to work. However, ambulatory urodynam- ics revealed nonvoiding detrusor con- tractions during the filling phase in up to 69% of healthy volunteers, 1,2 sug- gesting that these contractions may be a normal physiological mechanism. Currently to our knowledge differ- ences in NVCs between normal and 0022-5347/11/1862-0721/0 Vol. 186, 721-727, August 2011 THE JOURNAL OF UROLOGY ® Printed in U.S.A. © 2011 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION AND RESEARCH,INC. DOI:10.1016/j.juro.2011.03.123 www.jurology.com 721