Functional whole rat bladder model

There are many animal models that have been utilized for the study of urinary bladder function including the dog, cat, rabbit, and rat. Although the rat has been used extensively for the study of urinary bladder function, the relatively small size and capacity of the urinary bladder has made the functional evaluation of the bladder difficult. The present study describes an in vitro whole rat bladder preparation with which we were able to measure the following properties of urinary bladder function: (1) the pressure‐volume relationship (cystometry) of the isolated bladder; (2) intravesical pressure in response to pharmacological stimulation (isometric bladder contractility); (3) the ability of the bladder to expel its contents in response to pharmacological agents (isotonic contractility); and (4) the ability of the bladder to expand in response to pharmacological stimulation (isoproterenol). Bethanechol produced a dose‐related increase in intravesical pressure (“closed system”) in the isolated bladder. The maximal pressure response was inversely proportional to the initial volume of the bladder. Bethanechol also produced a dose‐related isotonic contraction of the bladder (“expulsion system”). Although bladders filled to one‐fourth, one‐half, three‐fourths, or full capacity were able to expel approximately 100% of their initial volume, there was a significant shift in potency. As the initial volume of the bladder increased, a higher concentration of bethanechol was required to empty the bladder. In general, the in vitro whole rat bladder model is a methodology by which bladder function can be evaluated. In this regard, it has significant advantages over isolated strip methodologies. With this model the ability of the bladder to empty, to generate intravesical pressure, and to relax can be measured. Prior studies have clearly demonstrated that the ability of isolated strips to contract may not accurately reflect the functional ability of the bladder to empty.