A VIP/PHI-containing pathway links urinary bladder and sacral spinal cord.

Nerve fibres containing VIP and the co-produced PHI are found in the dorsal horn and autonomic centres of the sacral spinal cord and in pelvic organs. We have investigated the origin of these nerve fibres and a possible peptide-containing pathway linking pelvic viscera with the spinal cord of the cat and rat using neurochemical and neurosurgical procedures, retrograde tracing and immunocytochemistry. Cell bodies were located in the dorsal root ganglia (after colchicine injection), pelvic ganglia and bladder wall. Capsaicin treatment induced a loss of VIP/PHI from the dorsal horn. Retrograde tracing from the bladder revealed True Blue labelled cells in the dorsal root ganglia (L6, S1), parasympathetic nuclei and pelvic ganglia. Labelled cells were sequentially immunostained for VIP/PHI which were numerous in pelvic ganglia and scattered and weak in dorsal root ganglia. Pelvic nerve section induced a decrease of VIP/PHI immunoreactivity from the spinal cord and no change or a minimal increase in immunoreactive nerve fibers of the bladder. Thus pelvic visceral afferents with cell bodies in the dorsal root ganglia are a significant source of VIP/PHI-containing fibres in the sacral dorsal horn.