The Use of Cystometry in Small Rodents: A Study of Bladder Chemosensation

Summary

Cystometry is an efficient technique to measure bladder function of small animals in vivo. The bladder is continuously infused at rates controlled through an intravesical catheter, whereas the urethra is left free for micturition. This allows for repetitive filling and emptying of the bladder, while intravesical pressure and voided volume are recorded.

Abstract

The lower urinary tract (LUT) functions as a dynamic reservoir that is able to store urine and to efficiently expel it at a convenient time. While storing urine, however, the bladder is exposed for prolonged periods to waste products. By acting as a tight barrier, the epithelial lining of the LUT, the urothelium, avoids re-absorption of harmful substances. Moreover, noxious chemicals stimulate the bladder's nociceptive innervation and initiate voiding contractions that expel the bladder's contents. Interestingly, the bladder's sensitivity to noxious chemicals has been used successfully in clinical practice, by intravesically infusing the TRPV1 agonist capsaicin to treat neurogenic bladder overactivity¹. This underscores the advantage of viewing the bladder as a chemosensory organ and prompts for further clinical research. However, ethical issues severely limit the possibilities to perform, in human subjects, the invasive measurements that are necessary to unravel the molecular bases of LUT clinical pharmacology. A way to overcome this limitation is the use of several animal models². Here we describe the implementation of cystometry in mice and rats, a technique that allows measuring the intravesical pressure in conditions of controlled bladder perfusion.

After laparotomy, a catheter is implanted in the bladder dome and tunneled subcutaneously to the interscapular region. Then the bladder can be filled at a controlled rate, while the urethra is left free for micturition. During the repetitive cycles of filling and voiding, intravesical pressure can be measured via the implanted catheter. As such, the pressure changes can be quantified and analyzed. Moreover, simultaneous measurement of the voided volume allows distinguishing voiding contractions from non-voiding contractions³.

Importantly, due to the differences in micturition control between rodents and humans, cystometric measurements in these animals have only limited translational value⁴. Nevertheless, they are quite instrumental in the study of bladder pathophysiology and pharmacology in experimental pre-clinical settings. Recent research using this technique has revealed the key role of novel molecular players in the mechano- and chemo-sensory properties of the bladder.

Protocol

1. Laboratory Animals

1. Animals (mice, rats) are housed in a specialized animal facility with a 12-hr light-dark cycle and ad libitum access to water and standard food pellets. Both age and sex of the animals are important parameters that should be standardized according to the needs. We typically perform cystometry in 10 - 12 week old female animals^5,6.
2. All animal experiments are carried out in accordance with the European Union Community Council guidelines and approved by the local ethics committee.

2. Anesthesia

1. Isoflurane anesthesia is used for performing small surgical procedur....

Discussion

The cystometry technique presented here allows performing in vivo measurements of bladder function in animal models. Rats are probably the most used animal model. Mice are more difficult to handle, but offer the advantage of using genetically manipulated animals. Because of the technical difficulty of using conscious mice, which tend to be very active resulting in loosening of the implanted catheter and changes in the intra-abdominal pressures that may influence the intravesical pressure, we advise to kee.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
urethane	Urethane, Sigma-Aldrich	315419	group 2B carcinogen
isoflurane	Isoba, Schering-Plough Animal Health
polyethylene catheter	Intramedic Polyethylene tubing PE50, Becton Dickinson	427411
surgical microscope	Op-Mi 6, Carl Zeiss	Op-Mi 6
purse-string suture	Prolene 6/0, Ethicon	8610H
fascia and skin suture	Ethilon 4/0 or 5/0, Ethicon	662G or 661G
postoperative analgesics	Temgesic, Schering-Plough Animal Health		dosage for rats: 0.05 mg/kg
amplifier	78534c monitor, Hewlett Packard
analytical balances and balance data acquisition software	FZ 300i, A&D	FZ-300i
infusion pumps	pump 33, Harvard apparatus	HA33
cystometry recording system	Dataq instruments, DI-730 series and Windaq/Lite	DI-730-USB Windaq/Lite
temperature registration	Fluke 52 KJ thermometer	52 KJ
pressure transducers	Edwards Lifesciences, pressure monitoring set	T322247A