3,4-Dihydroxyphenylalanine and 5-Hydroxytryptophan as reserpine rntagonists.

Carlsson demonstrated that dopamine was a neurotransmitter in the brain and not just a precursor for norepinephrine. Digital facsimile from nature.com at this link.

In 2000 Arvid Carlsson shared the Nobel Prize in Physiology or Medicine with Paul Greengard and Eric R. Kandel "for their discoveries concerning signal transduction in the nervous system."