Saturable uptake of [3H]-tryptamine in rabbit platelets is inhibited by 5-hydroxytryptamine uptake blockers

[3H]-tryptamine is taken up by rabbit platelets through an active and saturable process which is temperature sensitive, sodium-dependent and inhibited by imipramine and non-tricyclic 5-hydroxytryptamine (5-HT) uptake blockers. There is an excellent correlation between the Ki for the inhibition of [3H]-tryptamine and [3H]-5-HT uptake in rabbit platelets for a series of 5-HT uptake blockers. These results indicate that [3H]-tryptamine is actively transported through the membrane of blood platelets by the same carrier that transports 5-HT.