The substance reaches wherever blood gets to, with exceptions when crossing the brain barrier. Most of the 5-HT receptors are in the brain though. It's not tru

The substance reaches wherever blood gets to, with exceptions when crossing the brain barrier. Most of the 5-HT receptors are in the brain though. It's not true for serotonin. Serotonin is to be released, taken back and metabolized locally, in and around the synapse. It doesn't travel around the body, at least in significant amounts, as hormones do.