Suppression of reflex urethral responses by sacral dermatome stimulation in an acute spinalized feline model

Abstract

Aims-Reflex contractions of the external urethral sphincter (EUS) are a major component of voiding dysfunction after neurological injury or disease. Aberrant urethral reflexes can prevent voiding and cause serious medical complications. Characterizing these urethral reflexes during genitourinary studies is necessary for evaluating novel pharmacological or neuroprosthetic approaches. The objectives of the present study were to generate urethral reflexes in the acute spinal feline, to quantify these reflexes, and to suppress them with electrical stimulation of the sacral dermatomes.Methods-This study comprised eight male cats. Anaesthesia was maintained with alphachloralose or sodium pentobarbital. The spinal cord was transected between T10 and T12, and nerve cuff electrodes were placed on the extradural S2 sacral roots to provide bladder activation. Bladder and urethral pressures were recorded during and after bladder contractions. Electrical stimulation was applied non-invasively to the sacral dermatomes with commercial surface electrodes.Results-Urethral reflexes were elicited consistently in six cats. The corresponding urethral pressure spikes were quantified. Putative metrics of urethral reflex activity such as the rate and average magnitude of reflex pressure spikes correlated significantly with standard urodynamic variables. Electrical stimulation of the sacral dermatomes suppressed urethral reflexes in three cats.Conclusions-These findings in an acute spinal feline preparation demonstrate a non-invasive means of suppressing undesirable urethral reflexes. Translation of this work to clinical use could improve neuroprostheses for restoring bladder function and enhance treatment of aberrant urethral reflexes in humans.

Electrical stimulation of sacral dermatomes can suppress aberrant urethral reflexes in felines with chronic spinal cord injury

“…These data provide a key step in validating previous results after acute SCI (19) and justify work to evaluate the voiding effectiveness of this novel approach to treat urethral sphincter spasticity.…”

“…Stimulus parameters found effective after chronic SCI were not tested in acute SCI, but the (.5 ON .5 OFF, 20 Hz) that was successful in acute animals (19) did not have a significant effect after chronic SCI. This suggests that the changes in the spinal reflex pathways from after chronic SCI could impact the afferent input required for reflex suppression.…”

“…Sacral dermatome levels more effectively deliver sensory stimulation to the spinal circuits generating unwanted urethral reflexes (19,21). To investigate surface localization effects, the L4 through S4 dermatomes were shaved and prepped with a medical depilatory prior to application of surface electrode patches.…”

“…Spike rate and spike amplitude were used as the primary measures of reflex EUS activity (19). Spikes were defined as pressure increases 1 standard deviation above a 0.5 second moving average, quantified in Matlab (Mathworks, Natick, MA).…”

“…Our group previously demonstrated that patterned dermatome stimulation reduces spastic urethral spike-activity in cats after acute spinal transection (19). Surface stimulation of sacral dermatomes provides a reversible, non-invasive technique that may be able to interrupt the aberrant urethral reflex pathway while retaining desirable bowel and sexual reflexes that are lost with rhizotomy.…”