ROLE OF THE TRIGONE IN MICTURITION

The exact function of the trigone in the act of micturition is not yet known, The current communication discusses its role, The myoelectric activity of the urinary bladder and trigone was studied in nine volunt eers (six women, three men; mean age 38.6 +/- 9.9 years) using Beekman suction electrodes. Two electrodes were applied to the bladder and on e to the trigone, The EMG and vesical pressure were recorded before an d during vesical filling and voiding. Slow waves or pacesetter potenti als (PPs) were recorded at rest from the detrusor and trigone, They ha d regular frequency and were followed randomly by bursts of action pot entials (APs), The frequency and amplitude of the trigonal PPs and APs were significantly lower than those of the vesical tissue. The mean P P frequency was 5.8 +/- 1.8 cycle/min (cpm) and amplitude 0.69 +/- 0.1 mV in the bladder and 3.4 +/- 1.2 cpm (P < 0.05) and 0.36 +/- 0.09 mV (P < 0,05), respectively, in the trigone, During vesical filling, nei ther the vesical pressure nor the vesical and trigonal PPs and APs reg istered significant differences from the resting stage (P > 0,05), Dur ing voiding, the vesical electric activity increased and presented as fast activity spikes or APs of high amplitude (mean 678.6 +/- 88.6 mu V). The trigonal electric activity showed no significant change (P > 0 .05) in comparison with the pre-evacuation status. These findings sugg est that the trigone does not contract during voiding, thus refuting t he claim that the trigone is responsible for preventing ureterovesical reflux on voiding.