Lidocaine prevents noxious excitation of bladder afferents induced by intravesical capsaicin without interfering with the ensuing sensory desensitization: an experimental study in the rat.

PURPOSE

The effects of the local anesthetic lidocaine on the noxious excitation and subsequent desensitization of bladder sensory fibers, produced by intravesical capsaicin, were evaluated through c-fos activation in the spinal cord.

MATERIALS AND METHODS

Noxious excitation was demonstrated by counting Fos-immunoreactive (IR) cells occurring in the rat spinal cord 2 hours after intravesical administration of 1 mM. capsaicin, preceded or not by 2% lidocaine. Desensitization was studied by comparing the number of Fos-IR cells induced by 1% acetic acid in rats treated 24 hours before with 1 mM. intravesical capsaicin preceded or not by 2% lidocaine.

RESULTS

Lidocaine instilled previously markedly reduced the number of Fos-IR spinal cells responding to capsaicin-induced bladder afferent excitation. Numbers of Fos-IR cells induced by acetic acid instillation in bladders desensitized by capsaicin administrated 24 hours before were not changed by lidocaine application prior to capsaicin.

CONCLUSIONS

These findings suggest that local anesthetic pretreatment of the bladder with lidocaine reduces the capsaicin-induced noxious excitation of the sensory fibers without decreasing their subsequent desensitization.