PRIMING OF 6-HYDROXYDOPAMINE-LESIONED RATS WITH L-DOPA OR QUINPIROLE RESULTS IN AN INCREASE IN DOPAMINE D-1 RECEPTOR-DEPENDENT CYCLIC-AMP PRODUCTION IN STRIATAL TISSUE

Priming with a dopamine agonist greatly enhances the behavioral effect iveness of dopamine D-1 receptor agonists in rats with 6-hydroxydopami ne lesions of the nigrostriatal pathway. The present study investigate d the influence of priming on cyclic AMP production in striatal slices . Stimulation of dopamine D-1 receptors with dopamine or the dopamine D-1 receptor agonist, -Cl-7,8-diol-2,3,4,5-tetrahydro-(1H)-3-benzazepi ne (SKF 81297), increased cyclic AMP production in the lesioned striat um of rats primed with L-3,4-dihydroxyphenylalanine (L-DOPA) by 329% a nd 405%, respectively, whereas in drug-naive rats the increase was 183 % and 187%, respectively. Priming with quinpirole produced similar res ults. It is suggested that priming with either L-DOPA or a dopamine D- 2 receptor agonist results in increased effectiveness of dopamine D-1 signal transduction, apparently not only related to previous stimulati on of D-1 receptors. (C) 1997 Elsevier Science B.V.