Reflex bladder activity induced by electrical stimulation of hind limb somatic afferents in the cat

Methods used and results obtained in a study of reflex responses of the bladder were as follows. Intravesical pressure was recorded continuously by the balloon method in chloralose--urethane anaesthetized cats. Various afferent fibres of hind limb cutaneous and muscle nerves were stimulated electrically, and the resulting changes in vesical functions were examined. It was found that: (1) when the bladder was nearly empty and quiescent, repetitive stimulation of group III (thin myelinated) and IV (non-myelinated) cutaneous or muscle afferent fibres of hind limb nerves caused a reflex increase in the vesical tonus. This somato-vesical excitatory reflex was propriospinal with its efferent are mainly in the pelvic nerves; (2) when there were spontaneous, large (amplitude above 300--400 mm H2O), rhythmic (about 1.0--2.5/min) micturition contractions of the expanded bladder, these contractions were inhibited by repetitive stimulation of the group III and IV cutaneous or muscle afferent fibres of hind limb nerves. The inhibition was sometimes followed by subsequent larger micturition contractions. The efferent arc for this somato-vesical inhibitory reflex was also in the pelvic nerves. Supraspinal structures were essential for producing the micturition contractions; (3) stimulation of group III and IV afferent fibres together was more effective than stimulation of the group III afferent fibres alone in activating either the excitatory or inhibitory somato-vesical reflex pathways.