5-HT (5-Hydroxytryptamine; Serotonin) is the neurotransmitter with the highest number of known receptors in humans, and the importance of 5-HT is also reflected in the number of species using 5-HT as a signalling molecule and the number of 5-HT receptors found within each species. 15 human 5-HT receptors have at this date been characterised and classified into seven 5-HT receptor families. Six of ...