A number of 1-arylpiperazines have been characterized as dired-acting serotonin agonists. Conformational parameters of this class that may affect receptor recognition and binding have been examined through the analysis of X-ray data and synthesis of rigid analogues. Radioligand binding studies indicate that 2, 3, 4, 4a, 5, 6-hexahydro-g-(tri-fluoromethyl)-M- pyrazino [l, Za] quinoline (13), an arylpiperazine that mimics the X-ray conformation of the ...