The rabbit as an intracavernous injection study model

We investigated the feasibility of using the rabbit as an animal model for intracavernous injection studies. The rabbit, having a penile structure rather similar to that of humans, offers the advantage of being a strain-specific, adequately sized, and easily controlled experimental animal. Using intracavernous injections of the two vasoactive drugs prostaglandin E₁ (PGE₁, 0.2-1.6 μg/kg) and papaverine (PAP, 0.25-1 mg/kg), which have been commonly used in the management of erectile dysfunction in man, increases intracavernous pressure (ΔICP) were induced. After intracavernous injection of PGE₁, the maximal ΔICP ranged from 18 to 44 mmHg (mean 29.25 ± 7.85 mmHg) with a duration of tumescence from 3.1 to 13.3 min (mean 8.61 ± 3.71 min). Intracavernous injection of PAP also induced increases in ICP, with a maximal ΔICP ranging from 24 to 56 mmHg (mean 43.5 ± 11.35 mmHg) and a duration of tumescence from 5.3 to 15 min (mean 10.25 ± 3.39 min). The systemic blood pressures were unchanged after all intracavernous injections. In addition, administration of cAMP antagonist in combination with PGE₁ inhibited the relaxing effects of PGE₁ in a dose-dependent manner. Our results suggest that the effects of vasoactive drugs on the rabbit's corpus cavernosum are similar to those in humans; thus the rabbit model is a suitable alternative for further physiological and pharmacological studies of penile erection.