Dopamine transporter imaging ligand
The 3.alpha. isomer of RTI-55, RTI-352, is an effective in vivo binding ligand that reflects greater selectivity for the dopamine transporter than is observed with RTI-55. In addition, there is also a more rapid achievement of apparent equilibrium in the striatal-to-cerebellar ratio (compared to RTI-55) as the ratio peaks at about 30 min and is maintained for about 20 min thereafter. Such apparent equilibrium is useful in developing an approach to measuring the number of dopamine transporters present in tissues. Moreover, these results indicate that the utilization of 3.alpha. isomers of a variety of 3.beta.-(substituted phenyl)tropanes will result in greater selectivity for dopamine transporters and a more rapid of achievement of apparent equilibrium.