Interaction of permanently charged metoclopramide analogs with D-2 dopamine receptors.

1. The binding of permanently charged benzamides to the D-2 dopamine receptor of striatal membranes was compared with that of tertiary amine benzamides. 2. The permanently charged benzamides were able to inhibit the binding of [3H]-spiperone to striatal membranes but were less potent than the corresponding tertiary amines. 3. Removal of sodium or decreasing the pH from 7.8 to 6.2 decreased the binding of all benzamides tested, but the permanently charged analogs were affected less by these changes than the tertiary amines. 4. These results suggest that while the binding properties of the permanently charged benzamides are similar to those of the tertiary amine benzamides, there are differences in the manner in which these compounds interact with the D-2 receptor.