A Avelino1, F Cruz, A Coimbra. 1. Institute of Histology and Embryology, Faculty of Medicine of Porto, IBMC of University of Porto, Portugal.
Abstract
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.
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.