Using strips of corpus cavernosum tissue from 21 male volunteers, the authors showed how the interaction of nitric oxide with the musculo/vascular system of the human penile corpora cavernosa initiated and maintained a penile erection. In this paper they used a drug designated ‘M&B 22948’ which is an inhibitor of cyclic guanosine monophosphate (GMP), to show that this drug has the same vasodilatory effect that nitric oxide has after its molecular interaction with the GMP/guanylate cyclase system on the penis. They determined that this drug was a ‘phosphodiesterase-5 (PD5), inhibitor’ and in doing so, they were the very first to observe the action of a PD5 inhibitor on the erection process. The discovery was commercialized with erection drugs such as Viagra and Cialis.

Order of authorship in the original publication: Rajfer, Aronson...Ignarro.

(Thanks to Juan Weiss for this reference and its interpretation.)