Cavernous Nerve Stimulation and Recording of Intracavernous Pressure in a Rat

Summary

This study describes a simplified surgical procedure and technique for performing cavernous nerve stimulation with the isolation of the nerve-electrode complex using silicone glue and intracavernous pressure measurement.

Abstract

The stimulation of the cavernous nerve (CN) and measurement of intracavernous pressure (ICP) have been used extensively to test and evaluate therapies for erectile dysfunction. However, the methods used vary between laboratories, and pitfalls still exist. The goal of this study was to describe a surgical technique that would provide a reliable and reproducible model. By exposing the ischiocavernosus muscle at its point of insertion on the ischial tuberosity, the penile crus could be cannulated with minimal dissection and injury to the structures involved in erectile function. Repeated stimulation of the CN, without the need for lifting and drying, was achieved by using a 125 µm bipolar silver electrode and biocompatible silicon glue to isolate the electrode-nerve complex. This method prevents neuropraxia by reducing stretching and drying the nerve and provides complete isolation of the nerve, negating electrical leakage and preventing stimulation of alternative pathways.

Introduction

In vivo study of erectile function in experimental animals started in 1863 with the pioneering experimental work of Eckhard¹. Electrostimulation of the pelvic nerves was used to induce the increased ICP in dogs. Throughout the 20^th century, similar experimental protocols were used in larger animals such as dogs, monkeys, cats and rabbits. Evaluating erectile function in a rat was first developed by Quinlan et al. in 1989². The method has since been modified and updated by several other groups³⁴. Today, the rat is the most widely used animal mode....

Protocol

Animals were housed in the University of Southern Denmark Animal Care Facility as per institutional guidelines. All animal experiments were carried out in accordance with the National Institutes of Health guide for the care and use of laboratory animals. This is an acute, non-survival surgery procedure. 

1. Preparation of Tubing, Electrode, and Instruments for the Surgical Procedure

1. Use the following microsurgical instruments: surgical scissors, angled micro scissors, a tissue forceps, a pair of Dumont #7 and #5 curved micro forceps, a micro needle holder, and retractors.
   Note: As this is an acute pr....

Results

The use of this protocol with the recommended stimulation settings, under inhalation anesthesia with isoflurane 2.0% oxygen 0.8 L/min, should produce results as shown in Figure 11 and Figure12, where there is multiple back to back stimulations between 75-80 mm Hg. Figure 13 shows the same stable response over a 20-min stimulation with the response stable at 73-77 mm Hg. Test the line for ICP meas.......

Discussion

The principal goal of this study was to describe a simplified surgical technique of penile crus cannulation for ICP recording and isolation of the CN for electrostimulation. We introduced modifications to the dissection of the cavernous body to simplify the surgery and provide reproducible recordings of the increase of the ICP with CN stimulation. With a 1 cm vertical skin incision, lateral to the base of the penis, using the palpable ischial tuberosity as guidance, we achieved good exposure of the ischiocavernosus muscl.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Adson forceps	Fine Science Tool	11006-12
Dumont #7 forceps	Fine Science Tool	11271-30
Dumont #5 forceps	Fine Science Tool	11273-20
ToughCut Mayo scissor	Fine Science Tool	14110-15
Miniature Vannas Spring scissor	Fine Science Tool	15006-09
Ultra Fine Hemostat	Fine Science Tool	13020-12
Crile Hemostat	Fine Science Tool	13004-14
Kwik-Sil Adhesive	World Precision Instruments	KWIK-SIL
Teflon coated silver wire 0.125 mm	World Precision Instruments	AGT0510
Elastic wire retractors	Custom made
Scalpel blade	Fine Science Tool	10023-00
PE-50 tubing	Warner Instruments	64-0753
23 G Needle	Kruuse	121272
SD-9 Square Pulse Stimulator	Somatco	1077/183
Blood pressure transducer and cable	World Precision Instruments	BLPR2
Raucotupf Cotton-tipped Applicators	Lohmann-Raucher	11966
Pro-ophta Ocular Sticks	Lohmann-Raucher	16515
NaCl 0,9 % 100 mL	Local pharmacy
Heparin	Local pharmacy
25 mL Syringe	Odense University Hospital
Vet eye ointment - Viscotears	Local pharmacy
silver wires	Science Products GmbH, Heidelberg, Germany
Silicon Glue	Kwik-Sil, World Precision Instruments, Sarasota, FL, USA