Changes in vesical function produced by cutaneous stimulation in rats

(1) The effect of stimulation of various skin areas on the function of the bladder was examined in anesthetized rats with the CNS intact, in decerebrated non-anesthetized rats and in spinal rats. The tone and contraction of the bladder was measured by the intravesical ballon method. (2) When the volume of the intravesical ballon was expanded so that the resting vesical pressure was increased from O to approximately 40 mm H2O level, the bladder revealed small spontaneous contractions in all experiments. Under these conditions intravesical pressure was increased approximately 40 mm H2O by application of tactile or nociceptive stimulation of the skin in the perineal area. This excitatory perneal-bladder response existed befor and after spinal transection and was shown to be a propriospinal reflex for which reflexly increased nerve discharges of vesical branches of the pelvic nerves were responsible. (3) When the volume of the intravesical ballon was further expanded so that the resting vesical pressure was kept about 200 mm H2O, the bladder had the usual large rhythmic contractions (micturition contractions) with amplitudes of about 610 mm H2O, and rhythms of 1--3/min in the CNS intact or decrebrated rats. These large contractions were driven by the rhythmic bust discharges of the vesical nerve branches of the pelvic nerves. The occurrence of the large contractions of the bladder could be inhibited by nociceptive stimulation which was localized in the perineal area. This inhibition of the large contractions was caused by disappearance of the rhythmic burst discharges in the vesical branches of the pelvic nerves. (4) On some occasions in the CNS intact anesthetized and in the decerebrated non-anesthetized rats the large contractions of the bladder disappeared during experiments even when the bladder was expanded enough for producing normal large contractions and kept at high intravesical pressure. Regardless of whether the large contractions existed or not at the high intravesical pressure, the vesical pressure was increased by perineal stimulation due to the same neural mechanism mentioned in (2) above.