Sensory Neuronal Change after Intravesical Electrical Stimulation in Spinailized Rat

The clinical benefits of intravesical electrical stimulation (IVES) in patients with increased residual urine or reduced bladder capacity have been reported. However, studies on the underlying mechanism of IVES has been limited to the A delta afferent and parasympathetic neurons. This study investigated the changes in the calcitonin gene-related peptide (CGRP), substance P (SP), and nitric oxide synthase (NOS) expression in the thoracolumbar and lumbosacral dorsal root ganglia (DRG) of spinalized rats to determine the effect of IVES on the C fiber afferent nerve. Forty Sprague-Dawley rats were divided into normal controls (n=10); IVES treated normal rats (n=10), spinalized rats (n=10), and IVES treated spinalized rats (n=10). IVES was performed for 2 weeks (5 days a week). IVES was started 3 weeks after spinalization in the spinalized animals. All animals had the DRG removed at the thoracolumbar (T13-L2) and lumbosacral (L5-S1) level. Changes in the CGRP, SP and n-NOS levels at the DRG were measured by western-blot analysis. The relative density of the CGRP and SP following spinalization was significantly higher compared to the controls in both the T13-L2 and L5-S1 DRG. However, IVES in the spinalized rat significantly decreased the relative density of the CGRP and SP compared to the rats with spinalization alone. A significant increase in the relative density of n-NOS was detected in the L5-S1 DRG following spinalization. However, the density of n-NOS was significantly lower after IVES in both the T13-L2 and L5-S1 DRGs. In conclusion, IVES significantly reduced the CGRP, SP and n-NOS levels in the DRG of spinalized rats. CGRP, SP and n-NOS are the main factors that contribute to the hyperexcitability of the micturition reflex after spinal cord injury. These results suggest that the bladder C fiber afferent is also involved in modulating the micturition reflex by IVES.

Subpoblaciones neuronales presentes en el ganglio de la raíz dorsal / Neuronal subpopulations present in the dorsal root ganglion

La función principal de las neuronas del ganglio de la raíz dorsal (GRD) es transmitir la información sensorial desde la periferia hasta el sistema nervioso central. Dos clases de la célula están presentes en el ganglio: las células no neuronales y las neuronales. La heterogeneidad morfológica, fisiológica y bioquímica de la población neuronal permite diferenciarla en subpoblaciones. Morfológicamente, se distinguen tres tipos neuronales (A, B y C) según el tamaño y las características ulraestructurales. Fisiológicamente, hay una relación directa entre el tamaño, el diámetro de las fibras nerviosas y la velocidad con que conducen el impulso nervioso. Finalmente, el uso de marcadores (neuropéptidos, enzimas, receptores, etc.) permite realizar una clasificación bioquímica, que es la más utilizada para estudiar la función neuronal. Este artículo revisa la evidencia experimental sobre el tema de la heterogeneidad neural del GRD y presenta una correlación desde el punto de vista bioquímico y fisiológico en los casos en donde hay información disponible. El estudio de subpoblaciones en este ganglio resulta de bastante interés para investigaciones en neurociencias principalmente en infecciones por virus neurotrópicos, traumatismos del nervio periférico y el estudio de factores neurotróficos, entre otros

Lack of in vitro spontaneous activity following axotomy of hamster sensory neurones.

Although peripheral axotomy of dorsal root ganglion cells in mice, rats and cats has been reported to generate spontaneous activity in sensory nerves, we did not find evidence for such activity in the hamster. In vitro, intracellular recording from L6-S1 dorsal root ganglion cells up to 6 weeks after axotomy did not reveal any evidence for either increased membrane excitability or spontaneous activity. Also, in the sciatic nerve-sectioned hamsters, there was a total absence of the self-mutilatory behaviour which has been reported in other rodents. These results support the hypothesis that species specific factors are important for the development of ongoing activity in sensory nerves following injury.