Postglomerular vasoconstriction induced by dopamine D-3 receptor activation in anesthetized rats

In the present study we investigated the renal hemodynamic effects of dopam ine Ds receptor activation by R(+)-7-hydroxy-dipropylaminotetraline (7-OH-D PAT) in thiopental-anesthetized Sprague-Dau ley rats. In clearance experime nts infusion of 7-OH-DPAT (0.01-1.0 mu g kg(-1) min(-1)) dose-dependently e levated glomerular filtration rate (GFR) without affecting mean arterial bl ood pressure (MAP). In renal blood dow experiments 7-OH-DPAT, infusion 1.0 pg kg-l min(-1) increased GFR by 16 +/- 2%, associated with an unexpected f all in renal blood fl by 20 + 3% and a significant elevation of renal vascu lar resistance by 18 + 3%. The renal hemodynamic changes were not influence d by pretreatment with the D-2-receptor antagonist S(-)sulpiride hut were c ompletely abolished during D-3 receptor inhibition by 5,6-dimethoxy-2-(di-n -propylamino)indane (U-99194A). In micropuncture experiments 7-OH-DPAT (1.0 pg kg(-1)-min(-1)) significantly elevated stop-flow pressure measured in t he early proximal tubules and reduced hydrostatic pressure at the first bra nching point of the efferent arteriole without altering MAP. We conclude fr om these data that pharmacological activation of dopamine D-3 receptors aff ects renal hemodynamics in anesthetized rats by preferential postglomerular vasoconstriction.