Systemic administration of fluorogold for anatomical pre-labeling of autonomic and motor neurons in the rat spinal cord compromises urodynamic recordings in acute but not long-term studies

Aims The use of anatomical tracer injections into peripheral tissues for retrograde labeling of spinal cord neurons may compromise physiological experiments in combined functional and morphological studies. Methods We investigated whether a systemic injection of a retrogradely transported tracer, fluorogold (FG), may provide an alternative to direct injections into end organs for combined anatomical and physiological studies of the lower urinary tract. Urodynamic studies including cystometrogram recordings and external urethral sphincter electromyography were used as functional outcome measures. Results Pre-labeling of spinal cord neurons by intraperitoneal (i.p.) administration of FG resulted in a transient decrease in voiding efficiency, increase in resting pressure as well as increase in bladder size and weight at 5-7 days after the tracer administration. In contrast, there were no urodynamic or end-organ effects detected at 6-8 weeks after the i.p. injection of FG. Conclusions We suggest that pre-labeling of spinal autonomic and motor neurons using i.p. administration of FG may be a useful tool when combining anatomical and functional outcome measures in long-term but not acute studies.