Changes in vesical function produced by cutaneous stimulation in rats

Abstract (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 balloon method. (2) When the volume of the intravesical balloon was expanded so that the resting vesical pressure was increased from 0 to approximately 40 mm H 2 O level, the bladder revealed small spontaneous contractions in all experiments. Under these conditions intravesical pressure was increased approximately 40 mm H 2 O by application of tactile or nociceptive stimulation of the skin in the perineal area. This excitatory perineal-bladder response existed before 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 balloon was further expanded so that the resting vesical pressure was kept about 200 mm H 2 O, the bladder had the usual large rhythmic contractions (micturition contractions) with amplitudes of about 610 mm H 2 O, and rhythms of 1–3/min in the CNS intact or decerebrated 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.