The effect of subatmospheric pressure on the simian penis.

The effects of subatmospheric pressure on the simian penis were studied in nine monkeys under anesthesia. A plastic cylinder was placed over the penis and suction applied until the gauge pressure was -100 to -200 cm. H2O. The intracavernous pressure decreased within one to three seconds to between -60 and -120 cm. H2O followed by a gradual increase as a result of blood flow into the corpora cavernosa. The intracavernous pressure recovery was 50% after 17 seconds and 100% by 30 to 60 seconds. These effects could also be observed when the penile base was partially constricted with a rubber band before applying the partial vacuum. Tumescence resulting from suction disappeared immediately when suction was terminated unless the base of the penis was constricted before and after the application of vacuum. In the latter case tumescence was prolonged (cavernous pressure between 60 and 120 cm. H2O) after suction. The cross-sectional area of the penis expanded to more than 150% of the flaccid state. The increase of intracavernous pressure from intracavernous papaverine injection was similar to that after suction with a constricting rubber band in place at the base of the penis. Subatmospheric pressure induces an expansion of the penis followed by increased blood inflow. The additional volume can be kept in the penis only if a constriction device is placed at the base of the penis. The tumescence induced by suction is passive, occurring without evidence of smooth muscle relaxation or release of neurotransmitters.