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

Abstract

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. This study comprised eight male cats. Anaesthesia was maintained with alpha-chloralose 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. 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. 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.