Botulinum neurotoxin (BoNT) has been used for years as a way to relax the smooth muscle of the bladder with bladder spasm.
BoNT is also thought to relax the smooth muscle that controls blood flow through the arteries of the penis; when the smooth muscle relaxes, the arteries increase in diameter, and more blood flows into the penis—causing improved erection and, perhaps, penile health.
BoNT also is known to migrate along the axon that innervates tissue (this is known to happen when BoNT is used to treat migraines).
It could be that this migration of BoNT along the ganglion to the controlling axon could increases parasympathetic tone–also contributing to increased firmness of the erection.
