Central 5-hydroxytryptamine (5-HT) receptors have been classified into four main families: 5- HT1, 5-HT2, 5-HT3, and 5-HT4, 2-7 although others, such as 5-HT5, 5-HT6, and 5-HT7, have been identified from cloning studies. 8-10 The 5-HT1 family comprises subtypes~-HT~ A, B-HT~ B,~-HT~ D, 5-HTl~, ll-l~ and 5-HT l~ l~(the 5-HTlc receptor has been reclassified as a member of the 5-HT2 family). The~-HT~ D receptor has recently attracted ...