5-carboxyamidotryptamine (5-CT) labeled with tritium. 5-CT is a tryptamine derivative closely related to the neurotransmitter serotonin. 5-CT acts as a non-selective, high-affinity full agonist at the 5-HT1A, 5-HT1B, 5-HT1D, 5-HT5A, and 5-HT7 serotonin receptors. It also binds the 5-HT2, 5-HT3, 5-HT6 serotonin receptors with lower affinity.