Discussion
pain
BLOOD, BLIND
The present study examined whether the serotonergic system plays a role in facial expressions of pain by depleting plasma Trp concentrations in healthy volunteers via ATD in a double blind, placebo-controlled within-subject design. Blood analysis showed a substantial reduction in total plasma Trp levels and in the Trp/LNAA ratio after ATD; thus, indicating a markedly reduced central 5-HT neurotransmission (Crockett et al. 