Similarity of distributions of spinal c-fos and plasma extravasation after acute chemical irritation of the bladder and the prostate

Purpose: Persistent pain in referred areas and voiding dysfunction are characteristic symptoms of chronic abacterial prostatitis. Since referred pain from visceral organs is considered a neurological event, it appeared reasonable to hypothesize that the persistent pain associated with prostatitis might also be explained by neural mechanisms. Neurogenic plasma extravasation and c-fos expression in the spinal cord, after chemical irritation of the rat prostate, was identified as a method to investigate the neurogenic aspect of prostatic inflammation. Materials and Methods: The distribution of plasma extravasation using Evans blue dye was determined after chemical irritation of the prostate and bladder of the rat, and the distribution of dye extravasation was analyzed, c-fos expression within the spinal cord was determined immunocytochemically after chemical irritation of the prostate, bladder and superficial somatic region determined by the dye extravasation as a referred pain area (tail root). Results: Chemical irritation of the prostate resulted in plasma extravasation in L5 to S2 dermatomes (primarily in L6 and S1). In rats receiving bladder irritation, the distribution of plasma extravasation showed a similar pattern to that observed in animals receiving prostatic irritation. Chemical irritation of the 3 structures resulted in expression of c-fos positive cells within the lumbosacral spinal cord. With each treatment the majority of c-fos positive cells were in the L6 and S1 segments. In all 3 groups the highest percentages of c-fos positive cells were observed in deeper laminae, including the dorsal commissure and sacral parasympathetic nucleus. Conclusions: Our results strongly suggest that referred pain status in inflammation of the bladder and prostate is neurogenically mediated. Based on these studies, there should be significant overlaps of nociceptive neurons within the spinal cord, which receive nociceptive inputs from pelvic soma and viscera.