This study examined the mechanisms underlying the effects of sacral neuromodulation on reflex bladder activity in chloralose anesthetized cats. Bladder activity was recorded during cystometrograms (CMGs) or under isovolumetric conditions. S1-S3 dorsal (DRT) or ventral root (VRT) were electrically stimulated at a range of frequencies (1-30 Hz) and at intensities relative to threshold (0.25T-2T) for evoking anal/toe twitches. Stimulation of DRTs but not VRTs at 1T intensity and frequencies of 1-30 Hz inhibited isovolumetric rhythmic bladder contractions; 5 Hz DRT stimulation during CMGs was optimal for increasing (P<0.05) bladder capacity (BC). Stimulation at 15 Hz was ineffective and 30 Hz elicited a weaker response to S1 DRT stimulation and no response to S2 DRT stimulation. Stimulation of the S1 DRT was more effective (increase BC to 143% and 163% of control at 1T and 2T, respectively) than S2 DRT stimulation (increase BC to 126% and 146% of control). Bilateral transection of the hypogastric or pudendal nerves did not change the inhibitory effect induced by S1 DRT stimulation. Repeated stimulation of S1 and S2 DRTs during multiple CMGs elicited a significant (P<0.05) increase in BC (to 155±13% of control) that persisted after termination of the stimulation. These results in cats suggest that the inhibition of reflex bladder activity by sacral neuromodulation occurs primarily in the central nervous system by inhibiting the ascending or descending pathways of the spinobulbospinal micturition reflex.
- sacral neuromodulation
- Copyright © 2012, American Journal of Physiology - Renal Physiology