Prolonged nonobstructive urinary retention induced by tibial nerve stimulation in cats

Abstract

Nonobstructive urinary retention (NOUR) is a medical condition without an effective drug treatment, but few basic science studies have focused on this condition. In α-chloralose-anesthetized cats, the bladder was cannulated via the dome and infused with saline to induce voiding that could occur without urethral outlet obstruction. A nerve cuff electrode was implanted for tibial nerve stimulation (TNS). The threshold (T) intensity for TNS to induce toe twitch was determined initially. Repeated (6 times) application of 30-min TNS (5 Hz, 0.2 ms, 4–6T) significantly ( P < 0.05) increased bladder capacity to 180% of control and reduced the duration of the micturition contraction to 30% of control with a small decrease in contraction amplitude (80% of control), which resulted in urinary retention with a low-voiding efficiency of 30% and a large amount of residual volume equivalent to 130% of control bladder capacity. This NOUR condition persisted for >2 h after the end of repeated TNS. However, lower frequency TNS (1 Hz, 0.2 ms, 4T) applied during voiding partially reversed the NOUR by significantly ( P < 0.05) increasing voiding efficiency to 60% and reducing residual volume to 70% of control bladder capacity without changing bladder capacity. These results revealed that tibial nerve afferent input can activate either an excitatory or an inhibitory central nervous system mechanism depending on afferent firing frequencies (1 vs. 5 Hz). This study established the first NOUR animal model that will be useful for basic science research aimed at developing new treatments for NOUR.

Superficial peroneal neuromodulation of nonobstructive urinary retention in cats

“…Syndrome) can be treated with sacral neuromodulation and therefore must have a neurologic dysfunction that contributes to their voiding problem. 3 The present experiments confirm and extend previous reports [10][11][12][13] that electrical stimulation of somatic afferent inputs to the spinal cord can elicit opposing changes in bladder function presumably by activating either inhibitory or excitatory mechanisms in the central nervous system. It is known that these opposing effects are not only produced by different afferent nerves but also by different frequencies of stimulation.…”

“…A funnel was used to collect the voided fluid in a beaker that was attached to a force transducer to record the volume. 10 The tibial nerve on the right side and the superficial peroneal nerve on the left side were dissected via skin incisions at the ankles for implantation of tripolar cuff electrodes (NC223pt; MicroProbe, Gaithersburg, MD). Each electrode was connected to an electrical stimulator (S88; Grass Medical Instruments, Quincy, MA) via a constant voltage stimulus isolator (SIU5; Grass Medical Instruments).…”

“…At the beginning of each experiment, uniphasic rectangular pulses (5 Hz frequency, 0.2 ms pulse width) were used to determine the intensity threshold (T) for TNS to induce toe twitches. Based on a recent study 10 in cats showing that prolonged TNS of 4 to 6T intensity and 5 Hz frequency can produce NOUR lasting at least 2 hours, 30-minute TNS was repetitively applied at 4 to 6T intensity in this study to produce NOUR.…”

“…This repetitive TNS protocol successfully induced NOUR in a previous study. 10 After each 30-minute TNS, a CMG without stimulation was performed to determine the voiding efficiency. Once the voiding efficiency was less than 50%, 2 to 3 control CMGs were performed to confirm the persistence and repeatability of NOUR.…”

“…Clinically, NOUR without an identifiable cause, that is, no nerve/muscle disease or damage, is classified as idiopathic, which includes many NOUR patients with unidentified functional changes in the central nervous system. Although myogenic/neurogenic animal models can be produced by bladder ischemia or pelvic nerve injury, 8,9 a recent study 10 in cats successfully produced an animal model of NOUR without nerve/muscle injury by prolonged stimulation of somatic afferent axons in the tibial nerve. This cat model of NOUR was used in the current study to determine if stimulation of the superficial peroneal nerve can reverse NOUR elicited by prolonged tibial nerve stimulation (TNS).…”