Inhibition of micturition reflex by activation of somatic afferents in posterior femoral cutaneous nerve

Key points Activation of afferents in the posterior femoral cutaneous nerve (PFCN) can reflexively induce efferent firing in the pudendal nerve and pudendal afferent firing via a motor–sensory coupling. Activation of pudendal afferent nerves can inhibit the micturition reflex, suggesting PFCN stimulation might also inhibit the micturition reflex. This study discovered a somato‐bladder inhibitory reflex elicited by electrical or tactile stimulation of cutaneous afferents in the PFCN, but excluded the involvement of pudendal nerves. This PFCN‐bladder inhibitory reflex could be utilized to develop new neuromodulation therapies for lower urinary tract disorders. Abstract This study determined if activation of somatic afferents in posterior femoral cutaneous nerve (PFCN) could modulate the micturition reflex recorded under isovolumetric conditions in α‐chloralose anaesthetized cats. PFCN stimulation inhibited reflex bladder activity and significantly (P < 0.05) increased bladder capacity during slow infusion of saline or 0.25% acetic acid (AA). The optimal frequency for PFCN stimulation‐induced bladder inhibition was between 3 and 10 Hz, and a minimal stimulation intensity of half of the threshold for inducing anal twitching was required. Bilateral pudendal nerve transection eliminated PFCN stimulation‐induced anal twitching but did not change the stimulation‐induced bladder inhibition, excluding the involvement of pudendal afferent or efferent axons in PFCN afferent inhibition. Mechanical or electrical stimulation on the skin surface in the PFCN dermatome also inhibited bladder activity. Prolonged (2 × 30 min) PFCN stimulation induced a post‐stimulation inhibition that persists for at least 2 h. This study revealed a new cutaneous‐bladder reflex activated by PFCN afferents. Although the mechanisms and physiological functions of this cutaneous‐bladder reflex need to be further studied, our data raise the possibility that stimulation of PFCN afferents might be useful clinically for the treatment of overactive bladder symptoms.