The working mechanism of intravesical electrical stimulation (IVES) was evaluated in alpha-chloralose anaesthetized cats and rats. IVES involved a direct activation of bladder mechanoreceptor afferents of the A delta type and as a consequence a central reflex activation of the detrusor. The detrusor response was abolished by bilateral transection of the S1-S3 dorsal roots and by intravesical instillation of lidocaine. The optimal stimulation frequency was 20 Hz. The results offer a theoretical rationale for the use of IVES as treatment of weak detrusor contractility in man.

Purpose: Intravesical electrical stimulation (IVES) has been used clinically to treat patients with voiding disorders. The aim of the present experimental study was to obtain objective evidence of a modulation of the micturition reflex by intravesical electrical stimulation (IVES).

Materials and Methods: Forty-one female rats, anesthetized by alpha-chloralose were used for the experiments. Intravesical electrical stimulation was given by a catheter electrode in the bladder (5 minutes of continuous stimulation at 20 Hz, 7 to 11 mA). The effect was evaluated by the change in cystometric micturition threshold volume.

Results: The threshold volume of the micturition reflex decreased significantly to 82% of controls after IVES (p<0.001; n=31). The effect was reversible and lasted for about 1 hour. The decrease was prevented by a transient blockade of the bladder nerves during IVES.

Conclusions: Intravesical electrical stimulation induced a prolonged modulation of the micturition reflex in anesthetized rats. The effect was due to activation of bladder mechanoreceptor afferents and remained long after the period of stimulation. It is proposed that the modulation was due to a prolonged enhancement of excitatory synaptic transmission in the central micturition reflex pathway. Such a modulation may underlie the curative effect of IVES in certain voiding disorders.

Intravesical electrical stimulation (IVES) is used clinically to improve bladder evacuation in patients with inadequate micturition contractions. The procedure involves field stimulation of A bladder mechanoreceptor afferents resulting in a prolonged enhancement of the micturition reflex. The aim of the present experimental study in the rat was to identify the site for this neuromodulation, whether it was due to sensitization of bladder mechanoreceptors, to enhancement of transmission in the central micturition reflex pathway, or to improved effectiveness of the peripheral motor system of the bladder. The experiments were performed on female rats, anesthetized by -chloralose. Multi-unit afferent or efferent activity was recorded from bladder pelvic nerve branches during repeated cystometries before and after IVES. The specific antagonist CPPene was used to block central glutaminergic receptors of NMDA type. Micturition threshold volume decreased significantly after IVES. The afferent threshold volume, peak response, and pressure sensitivity were unchanged as were the peak efferent activity and bladder contractility. There was no efferent activity until just before the micturition contraction. The IVES-induced decrease in micturition threshold was blocked by prior administration of the NMDA (N-methyl-D-aspartic acid) antagonist CPPene (3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphonic acid). The findings indicate that the IVES-induced modulation of the micturition reflex is due to an enhanced excitatory synaptic transmission in the central micturition reflex pathway. The observed modulation may account for the clinical beneficial effect of IVES treatment.

OBJECTIVE: To determine whether induced bladder contractions influence the modulation by intravesical electrical stimulation (IVES) of the micturition reflex in anaesthetized rats, and to identify the optimal IVES frequency and duration.

MATERIALS AND METHODS: Seventy-six adult female rats, anaesthetized by alpha-chloralose. were divided into four groups to study the effect of: (i) IVES in combination with bladder contractions; (ii) bladder contractions alone; (iii) IVES frequency; and (iv) IVES duration. IVES was administered using a catheter electrode in the bladder. The effect of various IVES procedures was evaluated by determining the micturition threshold volume obtained from repeated cystometries before and after stimulation.

RESULTS: Administering IVES with standard parameters induced a significant decrease in the micturition threshold volume for about an hour. There was no difference in outcome between IVES with the bladder filled and contracting during the stimulation or empty and not contracting. Imposed bladder contractions per se had no effect on the micturition threshold volume. IVES at low frequencies (< or = 20 Hz) had a better modulatory effect than higher frequencies and the optimum duration of IVES was 5 min.

CONCLUSIONS: Evoked bladder contractions did not improve the IVES-induced modulation of the micturition reflex. These findings might help to improve the clinical application of the IVES procedure.

Objective

To determine whether induced bladder contractions influence the modulation by intravesical electrical stimulation (IVES) of the micturition reflex in anaesthetized rats, and to identify the optimal IVES frequency and duration.

Materials and methods

Seventy-six adult female rats, anaesthetized by α-chloralose, were divided into four groups to study the effect of: (i) IVES in combination with bladder contractions; (ii) bladder contractions alone; (iii) IVES frequency; and (iv) IVES duration. IVES was administered using a catheter electrode in the bladder. The effect of various IVES procedures was evaluated by determining the micturition threshold volume obtained from repeated cystometries before and after stimulation.

Results

Administering IVES with standard parameters induced a significant decrease in the micturition threshold volume for about an hour. There was no difference in outcome between IVES with the bladder filled and contracting during the stimulation or empty and not contracting. Imposed bladder contractions per se had no effect on the micturition threshold volume. IVES at low frequencies (≤20 Hz) had a better modulatory effect than higher frequencies and the optimum duration of IVES was 5 min.

Conclusions

Evoked bladder contractions did not improve the IVES-induced modulation of the micturition reflex. These findings might help to improve the clinical application of the IVES procedure.

1. Prolonged modulation of the parasympathetic micturition reflex was studied in cats anaesthetized by -chloralose. Reflex discharges were recorded from a thin pelvic nerve filament to the bladder and evoked by stimulation of the remaining ipsilateral bladder pelvic nerves or urethral branches of the pudendal nerve.

    

2. Stimulation of bladder or urethral afferents at A intensity evoked micturition reflexes with a latency of 90-120 ms. Such reflexes were much enhanced following repetitive conditioning stimulation of the same afferents at 20 Hz for 5 min.

    

3. The reflex enhancement lasted more than 1 h after the conditioning stimulation. The effect was not prevented by a preceding complete transection of the sympathetic supply to the bladder. A prolonged suppression of the reflex was obtained after conditioning stimulation of afferents in the dorsal clitoris nerves.

    

4. It is proposed that the prolonged modulations of the micturition reflex represent physiological adaptive processes, which preserve a flawless function of the bladder during life. The observations provide a theoretical explanation for the beneficial effect of electric nerve stimulation in patients with voiding disorders.