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 micrograms/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 (delta ICP) were induced. After intracavernous injection of PGE1, the maximal delta ICP 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 delta ICP 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.