ROLE OF CYCLIC ADENOSINE-MONOPHOSPHATE IN PROSTAGLANDIN E(1)-INDUCED PENILE ERECTION IN RABBITS

To investigate the role of cyclic adenosine monophosphate (cAMP) in pe nile erection in relation to the effect of prostaglandin E(1) (PGE(1)) , male adult New Zealand white rabbits were utilized as a model to stu dy intracavernous pressure (ICP) in vivo. After intracavernous injecti on of PGE(1) (0.2-1.6 mu g/kg) and 8-bromocyclic adenosine monophospha te (8-Br-cAMP, 0.5-1.5 mg/kg), both drugs raised the ICP in a dose-dep endent manner. The increased ICPs induced by PGE(1) and 8-Br-cAMP were 33.4 +/- 8.12 and 24.1 +/- 4.9 mm Hg, respectively (p < 0.05, paired Student's t test). Administrations of cyclic adenosine monophosphothio ate, Rp-isomer (cAMP antagonist, 0.02-0.08 mu mol/kg) prior to PGE(1) injections inhibited the effect of PGE(1) in vivo in a doss dependent manner. The systemic blood pressures and heart rates in rabbits were u nchanged during all the intracavernous injections. The corpus cavernos al tissues isolated from rabbits were studied for the cAMP contents af ter incubation of different doses of PGE(1) in vitro. The cAMP content s were also elevated in a manner parallel with the increases in PGE(1) concentrations (3-9 mu M). We conclude: (1) the feasibility of intrac avernous injection of vasoactive drugs is similar to that in man, thus the rabbit can be used as a suitable alternative for the studies of p enile erection, and (2) cAMP is mediated in PGE(1)-induced relaxation of the rabbit corpus cavernosum, and the cAMP system only participates partially in penile erection.