Vascular changes during penile erection in the dog.

1. The vascular effects of pelvic nerve stimulation on the penis were studied in dogs anaesthetized with sodium pentobarbitone and halothane. Changes in pressure and blood flow were measured through scalp vein needles inserted into the erectile bodies. 2. The penis contains two types of erectile body, which responded independently during erection induced by pelvic nerve stimulation. Pressure in the corpus spongiosum increased immediately upon stimulation, but only reached one-third of the more delayed pressure response of the corpora cavernosa. 3. At rest, arterial inflow resistance into the corpora cavernosa was high, whereas venous outflow resistance was low. Pelvic nerve stimulation (10-50 V, 10-16 Hz, 1 ms) caused an immediate increase in arterial flow, an increase in corpus cavernosal pressure (CCP), and a decrease in venous outflow. Saline infusion experiments showed there was active venous occlusion. Upon cessation of stimulation, these parameters returned to pre-stimulation levels. 4. The time taken to reach 50% of maximum change in arterial inflow was significantly less than for CCP, which was significantly less than for venous outflow. Occlusion of the aorta 1 min after cessation of stimulation decreased the pressure in the arterial tree supplying the corpora cavernosa, but CCP remained elevated, indicating that both inflow and outflow resistances were high. Thus, inflow resistance had returned to its pre-stimulation state before outflow resistance. 5. Direct measurements of blood flow through the corpus cavernosum were made with a hydrogen probe. There was a transient increase in blood inflow as CCP increased during pelvic nerve stimulation. There was some blood flow while CCP was elevated, indicating that the venous occlusion was not complete. 6. Sympathetic chain stimulation caused an increase in arterial resistance, and a decrease in CCP and venous resistance. 7. Infusions of acetylcholine (330 micrograms min-1) and vasoactive intestinal polypeptide (1-3.3 micrograms min-1) decreased arterial resistance and increased CCP and venous resistance. 8. This study suggests that during pelvic nerve-induced erection, arterial flow into the corpus cavernosum increases, followed by an increase in CCP and an actively controlled decrease in venous outflow.(ABSTRACT TRUNCATED AT 400 WORDS)