The current study was performed to determine the effect of calcium store depletion with cyclopiazonic acid (CPA) on the pre- and postglomerular vasoconstrictor responses to angiotensin II (ANG II) and norepinephrine (NE). CPA treatment significantly attenuated the afferent arteriolar response to 10 nM ANG II by 51% and to 1000 nM NE by 19%. Efferent arteriolar responses to ANG II and NE were also greatly attenuated in the presence of CPA. These data demonstrate that afferent and efferent arteriolar responses to ANG II and NE depend on release of calcium from CPA-sensitive intracellular stores. Furthermore, the postglomerular response to these agents exhibits a greater dependency on calcium release from intracellular stores. © 2001 Elsevier Science Inc. All rights reserved.