Is there a way to intentionally cause erectile dysfunction in a man whose penis works normally?

e.g. perhaps damaging the muscles that close the blood egress from the penis, so that they can't keep blood in the penis (which I believe is necessary for erection).

Sniffing Amyl Nitrate (a vasodialator) apparently has this effect: it dialates the blood vessels in the penis so that blood can get out, thus making it hard/impossible to have an erection.

From http://www.impotence.org/confront/howoccur.asp :

As the chambers (corpora cavernosa) fill with blood, they expand and exert strong pressure against the veins that normally drain blood from the penis. This pressure closes the veins, trapping blood in the penis. With more blood flowing in and less blood flowing out, the penis hardens, producing an erection.

Also from that site (snips):

During sexual arousal, nerve messages begin to stimulate the penis. Sexual function, including erectile function, originates in the brain.

It is important to note: An erection is a complex chain of events, involving the brain, blood vessels, nerves, and smooth muscle inside the penis. If any of these systems do not work properly, a man may not be able to get an erection.

- Jim

Slave-Jim is so right,

Also taking an antiandrogen like Androcur will cause your Testosterone to drop to nothing but if all the things Slave-Jim said work yes you can still get an erection, the most important is the brain.

I am a eunuch and had one hell of an erection last weekend