비아그라가 시간, 스트레스 및 돈을 절약할 수 있는 방법
Sexual stimulation that causes an erection results in the output and launch of nitric oxide in the penis. Nitric oxide causes an enzyme, guanylate cyclase, to produce cyclic guanosine monophosphate (cGMP) that is generally chargeable for raising and reducing the size of blood vessels carrying blood to and within the penis and triggering an erection