Inhibition of synaptosomal 5‐[3H]hydroxytryptamine uptake by endogenous factor(s) in human blood

Abstract
The inhibition of 5-[3H] hydroxytryptamine uptake into rat forebrain synaptosomes by human plasma extracts was studied. Highly potent, small (M r < 10000), and heat stable factor(s) were found to inhibit 5-[3H] hydroxytryptamine uptake specifically, reversibly and in a non-competitive manner. The possible role of these factor(s) as endogenous modulators of serotonergic activity is discussed.