INVIVO RECEPTOR-BINDING - ATTEMPTS TO IMPROVE SPECIFIC-NON-SPECIFIC RATIOS

In vivo receptor binding was examined using 3H-spiperone and 3H-pimozide for dopamine receptors and 3H-LSD for serotonin receptors. Two strategies for improving total: nonspecific binding ratios were tested. The first was to deplete endogenous ligands by various pharmacological treatments prior to 3H-ligand administration in an attempt to increase specific receptor binding; the second was to perfuse the brain with ice-cold saline after 3H-ligand administration in an attempt to reduce nonspecific binding. Alteration of dopamine and serotonin by administering d-amphetamine, reserpine, alpha-methyl-paratyrosine or parachlorophenylalanine did not significantly elevate striatal: cerebellar or cortical: cerebellar (measures of total: nonspecific) bonding ratios. However, perfusion with ice-cold saline significantly improved the ratios for both dopamine and serotonin receptors. Thus, cold saline perfusion may be of value in reducing blank values in autoradiographic and other studies requiring in vivo labelling of receptors. © 1979.