INVESTIGATIVE UROLOGY

Visualization of the neurovascular bundles and major pelvic ganglion with fluorescent tracers after penile injection in the rat
Davila HH, Mamcarz M, Nadelhaft I, Salup R, Lockhart J, Carrion RE
Department of Interdisciplinary Oncology at Moffitt Cancer Center, Division of Urology, University of South Florida, College of Medicine, Tampa, FL 33612, USA
BJU Int. 2008; 101: 1048-51

• Objective: To evaluate whether fluorescent tracers can consistently label the neurovascular bundles (NVBs) and major pelvic ganglion (MPG) after an intracavernosal penile injection, as the reported incidence of erectile dysfunction (ED) in men after radical prostatectomy (RP) is 55-65% and thus preservation of erectile function, sparing one or both of the NVBs remains one of the most vital factors.
• Materials And Methods: Male Sprague-Dawley rats (3 months old) received penile injections (20 microL; seven rats/group) of either deionized water (DW), Fluoro-Gold (FG), Fast-Blue (FB), Fluoro-Ruby (FR) or green fluorescent pseudorabies virus (GF-PRv). The rats were killed at 2, 3 and 14 days after injection and the NVBs and MPG were harvested and placed directly under fluorescence light. Image analysis was done by computer, coupled to a microscope equipped with a digital camera. Each NVB and MPG were analysed for its staining pattern and consistency.
• Results: When compared with the FB, FR and GF-PRv rats, the FG-injected rats had better staining of the NVB at 2, 3 and 14 days after injection. Under x200, FG highlighted the axons of the cavernous nerve (CN) and cell bodies (MPG). This indicates that FG injection into the penis induced the strongest CN labelling (positive staining) at 2 and 3 days after injection as compared with FB-, FR- and GF-PRv-injected rats.
• Conclusion: FG injection into the penis has consistent retrograde staining of the NVBs and MPG after 3 days. Therefore, we predict that FG could potentially be used to improve the identification of the NVB in other models. However, further studies need to be carried out before these tracers can be used in humans.
  
  
• Editorial Comment
  This is an interesting and promising study where the authors aimed to evaluate whether various tracer substances can consistently label the neurovascular bundles and the major pelvic ganglion after intracavernosal penile injection using the rat as an animal model. The results indicated that injection of fluoro-gold (FG) at the penis induces cell body labeling of neurons at the major pelvic ganglion at 2 and 3 days after the injection. Under fluorescent light, the penile injection of FG before pelvic surgery might help to identify the neurovascular bundles, and therefore, preserve potency after radical prostatectomy, for instances. We hope that it could be transposed to clinical setting soon.

Dr. Francisco J. B. Sampaio
Full-Professor and Chair, Urogenital Research Unit
State University of Rio de Janeiro
Rio de Janeiro, RJ, Brazil
E-mail: sampaio@urogenitalresearch.org