Action potential of the intramural ureter in the dog

In 33 adult mongrel dogs, the function of the intramural ureter was investigated. (A) Bipolar electrodes were placed in both the extravesical ureter and the intramural ureter. Then, an electromyogram (EMG) was recorded from two leads. (B) Cystotomy was performed, needle-type electrodes were inserted into the wall of the ureteral orifice and the extravesical ureter, and the EMG was recorded. (C) A special needle which could record EMG and measure pressure simultaneously was prepared. Then EMG and pressure measurements were recorded from the wall of the intramural ureter. In each experiment, action potentials were recorded from the intramural ureter that were similar to those from the extravesical ureter. The pressure in the wall of the intramural ureter showed variations matching the action potentials. From these results, it was evident that active muscle contraction occurred due to the action potential transmitted from the extravesical ureter even in the intramural ureter.