2-(N, N-di-n-propylamino) tetralin ([3H]-8-OH-DPAT), respectively. At the 5-HT2 receptor, the benzofurans had slightly decreased affinities, approximately one-third and one-sixth those of the indoles, for the primary amines and the tertiary amines, respectively. The benzofurans also had lower affinity at the 5-HTM receptor, but decreased only about 20-30% from that of the indole isosteres. Thus, the 5-HTM receptor is less discriminating with respect to ...