8b85b910_d_s_Flow___Scientific_American__2
[0] Sildenafil [1] Viagra, Cialis, Levitra [3] Blocking the enzyme that destroys cGNP also increases the amount of oxytocin in the brain. Sometimes called the “love hormone,” oxytocin facilitates emotional bonding. In addition, animal studies indicate that Viagra can increase blood flow and promote nerve growth in the brain, potentially alleviating depression. [2] 
Stimulating the penis produces cyclic guanosine monophosphate (cGNP), a chemical that dilates blood vessels. Viagra inhibits an enzyme that destroys cGNP, enabling more blood to flow to the organ.
Common Prescription Drugs Alter Blood’s Flow - Scientific American
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