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Animal Models of Erectile Dysfunction
Publication Name:
Current Protocols in Pharmacology
Unit Number:
Unit 5.41
DOI:
10.1002/0471141755.ph0541s29
Online Posting Date:
July, 2005 Abstract
The neuroanatomy of the rat, as well as the morphology of the rat corpus cavernosum, is well characterized. Several molecular biological methods, as well as in vitro preparations, are available for the corpus cavernosum (CC) from rats or mice, and functional investigations of the erectile tissues from these species have revealed similar responses to activation of nerves, endothelium, or pharmacological agents compared with other mammals. By recording intracavernous pressure (ICP), erectile responses to stimulation of nerves at peripheral sites can be evaluated objectively in anesthetized animals. It is thereby possible to isolate and study the effects of regulatory mechanisms of the autonomic nervous system on erection, and to quantify the effect of pharmacological modulation on nerve-induced responses as changes in ICP. In the conscious rodent model, erectile responses include activities in supraspinal and spinal regulatory units, which lead to activation of both autonomic and somatic pathways destined for the CC or the penile striated muscles. These components can be evaluated by recording ICP in conscious animals, allowing the investigator to avoid possible deleterious effects of anesthesia on supraspinal and spinal transmitter pathways that may be involved in the regulation of erection.
Table of Contents
- Unit Introduction
- Basic Protocol 1: Direct Measurement of Intracavernous and Intraarterial Pressures in the Anesthetized Rat
- Alternate Protocol: Direct Measurement of Intracavernous and Intraarterial Pressures in the Anesthetized Mouse During Erections
- Basic Protocol 2: Direct Measurement of Intracavernous Pressure in the Conscious and Freely Moving Rat During Erections
- Commentary
- Literature Cited
- Figures
- Tables
Materials
Basic Protocol 1: Direct Measurement of Intracavernous and Intraarterial Pressures in the Anesthetized Rat
Materials
- Heparinized saline: 100 IU/ml heparin (Leo Pharma) in 0.9% (w/v) NaCl
- Male rats (200 to 350 g)
- 20 mg/ml xylazine (e.g., Rompun, Bayer)
- 50 mg/ml ketamine (e.g., Ketalar, Parke Davis)
- Preoperative skin disinfectant (e.g., 5 mg/ml chlorhexidine (Fresenius Kabi), 70% isopropyl alcohol, alcohol prep pads)
- 0.9% (w/v) NaCl (normal saline)
- 3, 10, 30, 100, and 300 µg/kg apomorphine (Sigma)
- Methylene blue
- 1% mepivacaine (Carbocain, AstraZeneca)
- Platinum wire (1-mm diameter)
- Insulated copper wire (1- to 2-mm diameter)
- Soldering iron
- Heat-shrinking, electrically insulating rubber tubing (3-mm i.d.)
- Glass pipets (2- to 3-mm i.d., 1-mm wall thickness)
- Metal paper clip (medium size)
- Fine-metal file
- Rubber bands with circumference of ~10 cm
- PE-10 and -50 polyethylene tubing (Becton Dickinson)
- 23- and 27-G (1
1 2 in.) hypodermic needles (BD Microlance or equivalent) - Needle pins
- 1- and 5-ml syringes (e.g., Becton Dickinson)
- Pressure transducers (e.g., Spectramed Statham PE22 or equivalent)
- Digital chart recorder (e.g., Grass Instruments with Polyview software or equivalent)
- Three-way stopcocks (e.g., World Precision Instruments)
- Thermostatically controlled experimental table
- Dissecting microscope (e.g., Olympus)
- Cotton gauze compresses
- Cotton-tipped applicators
- Surgical tape (e.g., Johnson & Johnson)
- Scalpel handle for blades nos. 20 to 25 (e.g., World Precision Instruments)
- Scalpel blade, no. 22 (e.g., Swann-Morton)
- Operating scissors, 14.4 cm (e.g., Rudolf RU)
- Vannas microscissors, 7-mm blades (e.g., World Precision Instruments)
- McPherson-Vannas microscissor, 3-mm straight blades (e.g., World Precision Instruments)
- Tissue forceps, 12.5 cm, 1 × 2 teeth (e.g., World Precision Instruments)
- Adson forceps, 12 cm (e.g., World Precision Instruments)
- Dumont tweezers, 11 cm, 0.1 × 0.06 mm tip (e.g., World Precision Instruments)
- Dumont tweezers, 11 cm, 0.05 × 0.01 mm, 45° tip (World Precision Instruments)
- Olsen-Hegar needle holder, 14 cm (e.g., World Precision Instruments)
- Mosquito hemostatic forceps, 9 cm, straight (e.g., World Precision Instruments)
- 5-0 and 3-0 silk suture (e.g., Serag Wiessner)
- Crocodile clamps
- Square pulse stimulator (e.g., Grass Instruments S48 or equivalent)
- Tripod with holding arms (medium)
- Needlenose pliers
Alternate Protocol: Direct Measurement of Intracavernous and Intraarterial Pressures in the Anesthetized Mouse During Erections
Additional Materials (also see Basic Protocol 1 )
- Male mice (25 to 35 g)
Basic Protocol 2: Direct Measurement of Intracavernous Pressure in the Conscious and Freely Moving Rat During Erections
Materials
- Trochar (e.g., 1.40-mm i.d., 1.45-mm o.d.; World Precision Instruments)
- Woven surgical tape (e.g., Johnson & Johnson)
- Disposable butane lighter
- Rat metabolic cage
- 5-0 nonabsorbable polyfilament silk suture on a noncutting C-1 needle (Ethicon)
- Additional reagents and equipment for catheter construction, drug administration, and equipment set-up (see
Looking for materials? Suppliers Guide
Figures
-
Figure 5.41.1Electrode used for activation of the cavernous nerve. -
Figure 5.41.2Retractor made from a paperclip and a rubber band. -
Figure 5.41.3Intraarterial or intravenous catheter constructed from PE-10 and PE-50 tubing. -
Figure 5.41.4Intracavernous pressure catheter constructed from the modified end of a 23-G needle and PE-50 tubing. -
Figure 5.41.5Pressure transducer and connections to catheter and syringe via three-way stopcock. -
Figure 5.41.6Schematic of the equipment set-up and connections used for recording intracavernous pressure on activation of the cavernous nerve or administration of pharmacological agents in the anesthetized rat model. -
Figure 5.41.7The lateral portion of the prostate with the major pelvic ganglion (MPG) and cavernous nerve, as seen through the microscope. Parts of the adjacent bladder, seminal vesicle, and rectum are visible. -
Figure 5.41.8Microscope view of a PE-50 catheter positioned correctly in the left crus corpus cavernosum. -
Figure 5.41.9Intracavernous pressure (ICP) during stimulation of the cavernous nerve in a mouse. After stimulation, the time (D20) for ICP to decrease to 20% of maximal response (20) can be determined. BICP, basal intracavernous pressure; PICP, peak ICP; AUC, area under the curve; T80, time for the ICP to reach 80% (80) of PICP. -
Figure 5.41.10Intracavernous pressure in a mouse after intracavernous administration of Y27632, an inhibitor of Rho-kinase. -
Figure 5.41.11Intracavernous pressure (ICP) in a conscious rat after subcutaneous (s.c.) administration of apomorphine. Typical behaviors just prior to and during the erectile response may include washing (w), grooming (g), and yawns (y). TFR, time to first erectile response; AUC, area under the curve; PICP, peak ICP. -
Figure 5.41.12Dose-response relationship for number of erections observed over a 30-min period after subcutaneous administration of apomorphine in the conscious rat model. Data at each dose of apomorphine are from five to eight separate experiments. The doses of apomorphine are given in µg/kg, with the corresponding values in nmol/kg below.
Literature Cited
| Literature Cited | |
| Andersson, K.-E., Gemalmaz, H., Waldeck, K., Chapman, T., Tuttle, J.B., and Steers, W.D. 1999. The effect of sildenafil on apomorphine-induced increases in intracavernous pressure in the conscious rat. J. Urol. 161:1707-1712. | |
| Bivalaqcua, T.J., Usta, M.F., Matern, R.V., Sanabria, J., Champion, H., and Hellstrom, W.J.G. Gene transfer of endothelial nitric oxide synthase partially restores NO synthesis and erectile function in the streptozotocin diabetic rat. 2002. Int. J. Impot. Res. 14(Suppl. 4):S007 (P-008). | |
| Calabro, A., Italiano, G., Pescatori, E., Marin, A., Geatano, O., Abatangelo, G., Abatangelo, G., and Pagano, F. 1996. Physiological aging and penile erectile function: A study in the rat. Eur. Urol. 29:240-244. | |
| Chitaley, K., Webb, R.C., Dorrance, A.M., and Mills, T.M. 2001. Decreased penile erection in DOCA-salt and stroke prone-spontaneously hypertensive rats. Int. J. Impot. Res. 13(Suppl 5):S16-20. | |
| Christ, G.J., Rehman, J., Day, N., Salkoff, L., Valcic, M., Melman, A., and Geliebter, J. 1998. Intracorporal injection of hSlo cDNA in rats produces physiologically relevant alterations in penile function. Am. J. Physiol. 275:H600-H608. | |
| Dail, W.D. 1993. Autonomic innervation of male reproductive genitalia. In The Autonomic Nervous System—Nervous Control of the Urogenital System, Vol 6. (C.A. Maggi, ed.) pp. 69-101. Harwood Academic Publishers, London. | |
| De Groat, W.C. and Booth, A.M. 1993. Neuronal control of penile erection. In The Autonomic Nervous System—Nervous Control of the Urogenital System, Vol 6. (C.A. Maggi, ed.) pp. 465-513. Harwood Academic Publishers, London. | |
| Hart, B.L. and Melese-D'Hospital, P.Y. 1983. Penile mechanisms and the role of the striated penile muscles in penile reflexes. Physiol. Behav. 31:807-813. | |
| Hedlund, P., Alm, P., and Andersson, K.-E. 1999. NO-synthase in cholinergic nerves and NO-induced relaxation in the rat isolated corpus cavernosum. Br. J. Pharmacol. 126:349-360. | |
| Hedlund, P., Aszodi, A., Pfeifer, A., Alm, A., Hofmann, F., Fässler, R., and Andersson, K.-E. 2000. Erectile dysfunction in cGMP protein kinase I deficient mice. Proc. Natl. Acad. Sci. U.S.A. 97:2349-2354. | |
| Martinez-Pineiro, L., Brock, G., Trigo-Rocha, F., Hsu, G.L., Lue, T.F., and Tanagho, E.A. 1994. Rat model for the study of penile erection: Pharmacologic and electrical-stimulation parameters. Eur. Urol. 25:62-70. | |
| Mizusawa, H., Hedlund, P., Håkansson, A., Alm, P., and Andersson, K.-E. 2001. Morphological and functional in vitro and in vivo characterization of the mouse corpus cavernosum. Br. J. Pharmacol. 132:1333-1341. | |
| Mizusawa, H., Hedlund, P., and Andersson, K.-E. 2002. Alpha-Melanocyte stimulating hormone and oxytocin induced penile erection and intracavernous pressure increases in the rat. J. Urol. 167:757-760. | |
| Paxinos, G.T. and Watson, C. 1998. The Rat Brain in Stereotaxic Coordinates. Academic Press, New York. | |
| Quinlan, D.M., Nelson, R.J., Partin, A.W., Mostwin, J.L., and Walsh, P.C. 1989. The rat as a model for the study of penile erection. J. Urol. 141:656-661. | |
| Steers, W.D. 1994. Rat: Overview and innervation. Neurourol. Urodyn. 13:97-118. | |
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