Functional sequelae of cavernous nerve injury in the rat: is there model dependency.

INTRODUCTION: The rat model of cavernous nerve (CN) injury has been developed in an effort to define the functional and structural consequences of neural trauma in the corpus cavernosum. However, there is no universally accepted method of inducing nerve injury in this model, with neurotomy and crush models being used currently. To address this issue, we induced CN injury using various techniques in an effort to compare the hemodynamic sequelae of these injuries.
METHODS: Twenty-five adult male Sprague-Dawley rats were divided into five groups: (1) control: laparotomy only; (2) exposure: laparotomy and exposure of cavernous nerves bilaterally without nerve manipulation; (3) neurotomy; bilateral neurotomy; (4) bulldog crush: bilateral nerve crush with bulldog vascular clamp; and (5) hemostat nerve crush: bilateral nerve crush with a hemostat. Ten days later, a second operation was performed during which systemic mean arterial pressure (MAP) and intracavernosal pressure (ICP) were measured in response to CN stimulation proximal to the site of injury. Hemodynamic endpoints assessed included ICP/MAP ratio, rate of tumescence, and rate of detumescence.
RESULTS: The ICP/MAP ratio (mean +/- 95% confidence interval) in the control group was 70 +/- 4%. ICP/MAP ratios were significantly reduced in all CN injury groups compared with control group: exposure: 41 +/- 10% (P < 0.001); neurotomy: 35 +/- 15% (P < 0.001); bulldog crush: 39 +/- 13% (P < 0.001); hemostat crush: 31 +/- 9% (P < 0.0001). No significant difference existed in ICP/MAP ratios between the injury groups. Of note, the exposure group also demonstrated significant functional alterations. The rates of tumescence and detumescence were significantly reduced in all groups compared with the control group.
CONCLUSION: No significant difference in the magnitude and consistency of hemodynamic alterations has been demonstrated in all CN injury models assessed in this study.