INTRACAVERNOUS PRESSURE RESPONSES TO PHYSICAL AND ELECTRICAL STIMULATION OF THE CAVERNOUS NERVE IN RATS JAMIL REHMAN, GEORGE CHRIST, ARNOLD MELMAN, AND JONATHAN FLEISCHMANN ABSTRACT Objectives. To better define the techniques of nerve-sparing prostate dissection that would result in preservation of erectile function, we characterize the effects of physical pressure on the prostate and cavernous nerve, electrical stimulation of the cavernous nerve, and pharmacologic manipulations on intra- cavernous pressure (ICP) in normal and diabetic rats. Methods. Fischer-34 rats, both normal and diabetic, underwent dissections that isolated the cavernous bodies and cavernous nerves. Cavernous body pressures were characterized during surgical manipulation, during electrical stimulation of the cavernous nerves, and following papaverine hydrochloride injection. Results. In normal rats, baseline cavernous pressures ranged from 5 to 15 cm H 2 O (mean 12.29). In diabetic rats, the baseline pressure was significantly lower (3 to 7.5 cm H 2 O). Lateral nerve displacement caused ICP to rise to approximately 35 cm H 2 O in normal rats, but only to 20 cm H 2 O in diabetic rats. Electrostimulation resulted in cavernous pressure increases of 10-fold from baseline in normal rats and sevenfold from baseline in diabetic rats. ICPs were not disturbed appreciably with nerve-sparing dissection techniques. Neurotomy resulted in declines in baseline cavernous pressures in all rats. Electrostimulation of the distal end of a severed nerve resulted in pressure rises to 50% of those observed in rats with intact cavernous nerves. Intracavernous papaverine injection before or after nerve stimulation masked subsequent (expected) pres- sure changes. Conclusions. A change in cavernous pressure is a sensitive indicator of cavernous nerve manipulation. Both cavernous pressure measurements and electrostimulation of cavernous nerves may aid surgeons during radical prostatectomy. UROLOGY 51: 640–644, 1998. © 1998, Elsevier Science Inc. All rights reserved. W alsh and coworkers 1,2 popularized the ana- tomic approach to radical prostatectomy, a technique designed to spare the cavernous nerves and preserve erectile function. Impotence, how- ever, continues to be a postoperative consequence for many patients who undergo this operation, even if the nerves were thought to have been spared. Although vascular injury during prostatec- tomy contributes to impotence in some patients, unrecognized nerve injury is the probable cause for impotence in the majority of patients. To better define the limits of cavernous nerve manipula- tions, we explored the utility of intracavernous pressure (ICP) measurements under various surgi- cal and experimental conditions in rats. MATERIAL AND METHODS ANIMALS Two-month-old male Fischer-34 rats (Taconic Farms, Ger- mantown, NY) were fed Purina rodent chow ad libitum and housed individually with a 7 AM to 7 PM light cycle. The ani- mals were divided into three groups: group 1 consisted of control rats (n = 10); group 2 consisted of diabetic rats (n = 5); and group 3 consisted of rats who received physical and neurostimulation after intracavernous injection of papaverine hydrochloride (Eli Lilly) (n = 10). (A total of 10 diabetic rats were included at the outset of this study; 4 died within 3 months of induction of diabetes and 1 died during surgical dissection; therefore, the results of 5 diabetic rats are available for this study.) INDUCTION OF DIABETES Diabetes mellitus was induced for 3 months in 5 animals by one intraperitoneal injection of streptozotocin (STZ; 35 mg/ kg, Sigma Chemicals) dissolved in citrate buffer (0.1 M citric From the Department of Urology, Albert Einstein College of Med- icine/Montefiore Medical Center, Bronx, New York Reprint requests: Jonathan Fleischmann, M.D., Albert Einstein College of Medicine, Department of Urology, Weiller Hospital of AECOM, 1825 Eastchester Road, Room 2S 62, Bronx, NY 10461 Submitted: July 14, 1997, accepted (with revisions): October 14, 1997 BASIC SCIENCE © 1998, ELSEVIER SCIENCE INC. 0090-4295/98/$19.00 640 ALL RIGHTS RESERVED PII S0090-4295(97)00693-6