Glowing nerve network in pelvic region

Decoding the Nerve Network: What Elderly Cadavers Reveal About Pelvic Health

Kai Mendoza in Health & Wellness December 2025 • 5 min read.

"An innovative immunohistochemical study sheds light on the complex nerve composition of the hypogastric and pelvic splanchnic nerves, offering potential insights into pelvic health and aging."

The pelvic region's nerve network is vital for bladder control, sexual function, and bowel management. Key players in this network are the hypogastric nerve (HGN) and the pelvic splanchnic nerve (PSN). The HGN primarily carries sympathetic nerves, which control the body's "fight or flight" responses, while the PSN mainly contains parasympathetic nerves, responsible for "rest and digest" functions. Understanding how these nerves are organized and what types of nerve fibers they contain is essential for addressing various pelvic health issues.

Previous studies have examined these nerves in surgically removed specimens and fetuses, but a comprehensive analysis of both HGN and PSN in elderly individuals was lacking. This is a significant gap because the structure and function of nerves can change with age. New research has now investigated the composition of these nerves in elderly cadavers, using a technique called immunohistochemistry to identify different types of nerve fibers.

This article breaks down the findings of this study, explaining what types of nerve fibers were found in the HGN and PSN, and what these discoveries might mean for our understanding of pelvic health, aging, and potential treatments for nerve-related conditions.

Unveiling the Nerve Fiber Landscape: NOS, VIP, and TH

The research team examined tissue samples from the HGN and PSN of 12 elderly cadavers. They used immunohistochemistry to identify nerve fibers containing three key substances: neuronal nitric oxide synthase (NOS), vasoactive intestinal peptide (VIP), and tyrosine hydroxylase (TH). These substances act as markers, allowing scientists to differentiate between various types of nerve fibers. NOS and VIP are often associated with parasympathetic nerve function, while TH is typically linked to sympathetic nerve function.

The analysis revealed that the HGN near the sacral promontory (the upper part of the sacrum) was predominantly composed of TH-positive fibers, indicating a strong sympathetic component. In over 70% of fibers per bundle the HGN were positive for TH. NOS- and/or VIP-positive fibers were also present, but in smaller amounts (less than 10% per bundle).

HGN (Hypogastric Nerve): Dominated by sympathetic (TH+) fibers.
PSN (Pelvic Splanchnic Nerve): A mix of fiber types, with VIP+ often more prevalent than NOS+.
Fiber Distribution: No major differences in NOS+ and VIP+ fiber proportions within nerve bundles, suggesting limited target-dependent sorting in the studied regions.

In the PSN near the third sacral nerve root, the proportion of nerve fibers positive for NOS and/or VIP (or TH) was below 30%. The number of VIP-positive fibers was generally greater than that of NOS-positive fibers, and frequent co-localization of NOS and VIP. In both the HGN and PSN, there were frequent co-localization of NOS and VIP. More fibers in both nerves were positive for TH than for these other markers. More fibers in both nerves were positive for TH than for these other markers.

Implications and Future Directions

This study provides valuable insights into the nerve fiber composition of the HGN and PSN in elderly individuals. The findings suggest that the HGN primarily carries sympathetic fibers, while the PSN has a more mixed composition, with a greater proportion of VIP-positive fibers. Furthermore, the lack of distinct differences in NOS+ and VIP+ fiber distribution within nerve bundles suggests that target-dependent sorting of nerve fibers may not be prominent in these regions.

The researchers propose that the NOS+ and/or VIP+ fibers in the HGN are likely ascending postganglionic fibers to the colon, while those in the PSN root may be preganglionic fibers from Onuf's nucleus (a group of motor neurons in the spinal cord that controls the muscles of the pelvic floor).

This research opens doors for further investigation into the role of these nerve fibers in pelvic health and aging. Understanding how these nerves change with age could lead to the development of targeted therapies for pelvic floor disorders, bladder dysfunction, sexual dysfunction, and other related conditions.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.5115/acb.2015.48.2.114, Alternate LINK

Title: Composite Nerve Fibers In The Hypogastric And Pelvic Splanchnic Nerves: An Immunohistochemical Study Using Elderly Cadavers

Subject: Cell Biology

Journal: Anatomy & Cell Biology

Publisher: Korean Association of Anatomists

Authors: Hyung Suk Jang, Kwang Ho Cho, Keisuke Hieda, Ji Hyun Kim, Gen Murakami, Shin-Ichi Abe, Akio Matsubara

Published: 2015-01-01

Everything You Need To Know

What is the primary nerve fiber composition of the hypogastric nerve (HGN), and what does this tell us about its function?

The hypogastric nerve (HGN) primarily carries sympathetic nerve fibers, which are largely responsible for the body's 'fight or flight' responses. Analysis of the HGN in elderly cadavers showed that it was predominantly composed of tyrosine hydroxylase (TH)-positive fibers, indicating a strong sympathetic component. While neuronal nitric oxide synthase (NOS)- and vasoactive intestinal peptide (VIP)-positive fibers were present, they were in smaller quantities.

How does the nerve fiber composition of the pelvic splanchnic nerve (PSN) differ from that of the hypogastric nerve (HGN)?

The pelvic splanchnic nerve (PSN) has a more mixed composition of nerve fibers compared to the hypogastric nerve. The PSN contains both sympathetic and parasympathetic nerve fibers. The research indicates a higher prevalence of vasoactive intestinal peptide (VIP)-positive fibers compared to neuronal nitric oxide synthase (NOS)-positive fibers. The proportion of nerve fibers positive for NOS and/or VIP (or tyrosine hydroxylase (TH)) was below 30%.

What is immunohistochemistry, and how was it used in this study to analyze the nerve fibers in elderly cadavers?

Immunohistochemistry is a technique used to identify specific substances within tissue samples. In the study, it was used to identify nerve fibers containing neuronal nitric oxide synthase (NOS), vasoactive intestinal peptide (VIP), and tyrosine hydroxylase (TH). These substances act as markers, allowing scientists to differentiate between various types of nerve fibers and understand their distribution within the hypogastric nerve and pelvic splanchnic nerve.

What does the study suggest about target-dependent sorting of nerve fibers in the hypogastric nerve (HGN) and pelvic splanchnic nerve (PSN)?

The study's findings suggest that target-dependent sorting of nerve fibers may not be prominent in the hypogastric nerve (HGN) and pelvic splanchnic nerve (PSN) regions examined. This conclusion stems from the observation that there were no major differences in neuronal nitric oxide synthase (NOS)+ and vasoactive intestinal peptide (VIP)+ fiber proportions within nerve bundles. This implies that the destination or target of these nerve fibers may not significantly influence their distribution within these specific nerve regions.

What are the potential implications of this study's findings for treating pelvic health issues in the elderly, and what future research directions could build upon this work?

This research enhances our understanding of the nerve fiber composition within the hypogastric nerve (HGN) and pelvic splanchnic nerve (PSN) in elderly individuals, potentially leading to improved treatments for pelvic health issues. By identifying the primary nerve fiber types, like tyrosine hydroxylase (TH)+, vasoactive intestinal peptide (VIP)+ and neuronal nitric oxide synthase (NOS)+, in these nerves, researchers can develop more targeted therapies for conditions affecting bladder control, sexual function, and bowel management. Future studies can build on these findings to explore age-related changes in these nerves and to develop interventions that restore or enhance their function.