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

Area of Science:

• Neuroscience
• Autonomic Nervous System Research
• Visceral Pain Pathways

Background:

• Vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) are neurotransmitters found in nerve fibers within the sacral spinal cord's dorsal horn and autonomic centers, as well as in pelvic organs.
• The precise origin and pathways of these VIP/PHI-containing nerve fibers linking pelvic viscera to the spinal cord remain incompletely understood.

Purpose of the Study:

• To investigate the origin of VIP and PHI-containing nerve fibers in the sacral spinal cord.
• To elucidate the neural pathways connecting pelvic viscera to the spinal cord involving these peptides.

Main Methods:

• Neurochemical and neurosurgical techniques were employed in cats and rats.
• Retrograde tracing (True Blue) and immunocytochemistry were used to identify cell bodies and peptide localization.
• Capsaicin treatment and pelvic nerve section were performed to assess the role of specific pathways.

Main Results:

• Cell bodies for VIP/PHI-containing fibers were identified in dorsal root ganglia, pelvic ganglia, and the bladder wall.
• Capsaicin treatment led to a reduction in VIP/PHI in the dorsal horn, suggesting a role for capsaicin-sensitive afferents.
• Retrograde tracing from the bladder showed labeled cells in dorsal root ganglia and pelvic ganglia, with VIP/PHI being more abundant in pelvic ganglia.

Conclusions:

• Pelvic visceral afferents, originating from cell bodies in the dorsal root ganglia, represent a significant source of VIP/PHI-containing fibers innervating the sacral dorsal horn.
• These findings contribute to understanding the neuroanatomy and neurochemistry of visceral sensory pathways.