Characterization of laterality of innervation of the rat bladder

Retrograde axonal tracers were used to assess the laterality of bladder innervation which is unknown. Fluoro-Gold and Fast Blue were injected into the left and right bladder walls, respectively of male Wistar rats. The major pelvic (MPG), pelvic accessory (PAG), and dorsal root (DRG) ganglia were then removed and analyzed. 59% and 33% of the total labelled MPG cells were found in the ipsilateral and contralateral MPG (efferents), respectively. 65% and 31% of the total labelled PAG cells were found in the ipsilateral and contralateral PAG (efferents) respectively. The L1/L2 and L6/S1 DRG each received similar amount of ipsilateral innervation (45-52%) based on total labelled cells at each DRG level. 8%, 4%, and 4% of labelled cells in the MPG, PAG and DRG, respectively, contained both Fluoro-Gold and Fast Blue consistent with bilateral input originating from a single neuron. Immunohistochemistry showed that 40% of retrogradely labelled PAG cells were positive for tyrosine hydroxylase, far exceeding what has been shown for the MPG. Thus, assuming limited diffusion of tracers, the bladder receives a substantial crossed innervation especially in bladder afferents. This redundancy and bilateral neural input may contribute to preservation of bladder function and sensation even after extensive pelvic surgery.