Synthesis of new haloperidol analogues and characterization of their interactions with alpha-adrenoceptors in rat parotid slices and human platelet membranes.

1 The synthesis of several butyrophenone analogues of haloperidol is described. 2 The effects of these compounds on alpha-adrenoceptors were evaluated by examining their ability to reduce alpha 1-stimulated K+ release from rat parotid slices and to displace [3H]-phentolamine from human platelet membrane alpha 2-adrenoceptors. 3 The affinity of haloperidol and its analogues for alpha 1-receptors was found to be 1 to 2 orders of magnitude greater than that for alpha 2-adrenoceptors. These observations suggest that most of the alpha-adrenoceptor activity of butyrophenones results from their interaction with alpha 1-adrenoceptors. 4 The relatively high affinity of the butyrophenones for alpha 1-adrenoceptors suggests that they may be useful as probes in studies of alpha 1-adrenoceptors in these and other tissues.