A comparative study of voiding in the rat and the guinea pig;
simultaneous measurement of flow rate and pressure.
Asselt, E. Van, J. Groen, and R. Van Mastrigt.
Department of Urology-Urodynamics, Erasmus University Rotterdam,
Rotterdam, The Netherlands
APStracts 2:0023R, 1995.
In this study, the voiding phase of the micturition cycle in the
anesthetized rat and guinea pig is analyzed. In both animals, voiding
is characterized by an increase in intravesi cal pressure followed by
a decrease, accompanied by flow through the urethra and emission of
urine. An ultrasonic flow probe was used in both species to measure
the flow rate in relation to the intravesical pressure. In the (male)
rat, so-called high frequency oscillations are superimposed on the
decreasing bladder pressure. These oscillations do not occur in the
guinea pig. It is concluded that the high frequency oscil lations are
caused by intermittent flow and not by variations in the bladder
contraction. The intermittent flow most likely is caused by the
relaxation and contraction of the external urethral sphincter and may
have a function in territory mar king. In our view it is not likely
that the oscillations enhance bladder emptying as has been suggested
in the literature.
Received 2 June 1994; accepted in final form 22 January 1995
APS Manuscript Number R303-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.