Visceral-afferent signals from the cardiovascular system, but not urinary urge, affect startle eye blink

The aim of the current study was to investigate if startle methodology is suitable to reflect
urinary urgency. Eighteen healthy men were tested on two separate days, each including an
ingestion of fluid until 80% of the subjective urge to micturate was reached. EMG responses to
acoustic startle stimuli were assessed before and after micturition, as well as in the early and
late cardiac cycle phases (230 vs. 530 ms after a cardiac R-wave). Sonographic assessment
confirmed bladder-filling status. Emotional arousal, stress, urge and unpleasantness ratings, as
well as mean blood pressure were higher before than after micturition. Startle eye blink
responses were lower during the early than during the late cardiac cycle phase, but were not
affected by bladder filling status. We conclude that startle methodology is suitable for the
investigation of afferent signals from the cardiovascular system, but not to reflect urinary
urgency. This result may be due to different neurophysiological mechanisms underlying
afferent signals from the bladder compared to other visceral organs or interference with
affective states or sympathetic activation associated with bladder filling. Notwithstanding, the
present research protocol of fluid intake, sonographic assessment of the bladder, and subjective
reports, can be applied to examine visceral-afferent signals from the bladder.