Inhibitory and excitatory perigenital-to-bladder spinal reflexes in the cat

Abstract

This study revealed that in awake chronic spinal cord-injured (SCI) cats reflexes from perigenital skin area to the bladder can be either inhibitory or excitatory. Electrical perigenital stimulation at frequencies between 5 and 7 Hz significantly inhibited large-amplitude rhythmic reflex bladder activity, whereas frequencies between 20 and 40 Hz induced large-amplitude bladder contractions even at low bladder volumes when reflex bladder activity was absent. Both inhibitory and excitatory effects were enhanced as the stimulation intensity increased (5-30 V, 0.2-ms pulse width). During cystometrograms, the inhibitory stimulation (7 Hz) significantly increased the micturition volume threshold 35 Ϯ 13% above the control volume, while the excitatory stimulation (30 Hz) significantly reduced the threshold 21 Ϯ 3%. Mechanical perigenital stimulation applied by repeated light stroking of the perigenital skin with a cotton swab only induced an excitatory effect on the bladder. Both electrical and mechanical perigenital stimuli induced large-amplitude (Ͼ30 cmH 2O) bladder contractions that were relatively consistent over a range of bladder volumes (10 -90% of the capacity). However, the excitatory electrical stimulation only induced bladder contractions lasting on average 42.2 Ϯ 3.9 s, but the mechanical stimulation induced bladder contractions that lasted as long as the stimulation continued (2-3 min). Excitatory electrical or mechanical perigenital stimulation also induced poststimulus voiding. The ability to either inhibit or excite the bladder by noninvasive methods could significantly transform the current clinical management of bladder function after SCI. urinary bladder; electrical stimulation; spinal cord injury AFTER SPINAL CORD INJURY (SCI) incontinence occurs frequently due to detrusor overactivity. Meanwhile, the bladder also does not empty well due to detrusor sphincter dyssynergia resulting in a large residual volume of urine. Thus, the management of bladder function after SCI is a challenging task, because it requires inhibition of detrusor overactivity during urine storage and induction of a large-amplitude bladder contraction to empty the bladder (3). Current treatment for bladder dysfunction after SCI has either limited success (49) or requires major invasive spinal surgery to implant stimulating electrodes on spinal roots (6). Intermittent urethral catheterization is the most common method for managing urinary tract dysfunction (10). However, it can lead to frequent bladder infections (25).In this study in chronic paraplegic cats, we evaluated an alternative method to regulate bladder function involving electrical stimulation of somatic afferent nerves innervating the perigenital region. Perigenital-to-bladder reflexes undergo marked changes during postnatal development and after SCI. In neonatal kittens before the spinobulbospinal micturition reflex is fully developed, the bladder is emptied by the mother cat periodically licking the skin in the perigenital area of the kitten to induce a bladder contra...

Activation and inhibition of the micturition reflex by penile afferents in the cat

“…Also, perigenital electrical stimulation in the chronic spinal transected cat can activate and inhibit the bladder at similar frequencies as DNP stimulation (51). This method of stimulation in the female cat is likely activating the dorsal clitoral nerve, the female analog of the DNP, suggesting that the frequency-dependent bladder responses to electrical stimulation of the DNP observed in the intact and acute cat are still present in the chronic SCI cat.…”

Neural pathways involved in sacral neuromodulation of reflex bladder activity in cats

“…Electrical stimulation of perigenital skin area (27), vagina (16), or EUS (6) can also suppress bladder reflexes in animals presumably by inducing afferent firing in the pudendal nerve that in turn suppresses central micturition reflex pathways. Therefore, it is possible that sacral DRT stimulation could reflexively activate pudendal efferent nerves and induce contractions of EUS or vaginal muscles, which could in turn elicit pudendal afferent firing (14) and inhibit bladder activity.…”

“…Our previous studies in cats (25,27,29) have shown that pudendal nerve stimulation is frequency dependent, i.e., low frequency (3-10 Hz) is inhibitory but high frequency (20 -30 Hz) is excitatory. Meanwhile tibial nerve stimulation in cats (26) can inhibit bladder activity in a wide range of stimulation frequencies (5-30 Hz), but low frequency (5 Hz) is better than high frequency (30 Hz) in inducing acute inhibition during the stimulation.…”

A spinal GABAergic mechanism is necessary for bladder inhibition by pudendal afferent stimulation

“…Neural circuits in the periaqueductal gray (PAG) and pontine micturition center (PMC) are known to employ GABA (16) but are unlikely to be primarily responsible for pudendal stimulation-evoked reflex bladder inhibition, as bladder inhibition by pudendal afferent stimulation remains intact following chronic spinal cord injury (45,47). Any central GABAergic pathways that are involved would have also been antagonized after administration of intravenous picrotoxin.…”