We have earlier shown that treatment of A10 vascular smooth muscle cells (VSMC) with S-nitroso-N-acetylpenicillamine (SNAP); nitric oxide donor (NO) for 24h decreased the expression of natriuretic peptide receptor C (NPR-C) and adenylyl cyclase signaling, The present study was undertaken to examine the implication of different signaling mechanisms in NO-induced response. Treatment of A10 VSMC with SNAP decreased the expression of NPR-C and Gia-proteins in a time-dependent manner. The expression of Gia proteins was decreased at 6h, whereas the expression of NPR-C was attenuated at 2h. The NPR-C-mediated inhibition of adenylyl cyclase was attenuated (~50%) after 2h of treatment and was completely abolished after 6h of treatment. The decreased expression of NPR-C and NPR-C-mediated attenuation of adenylyl cyclase after 2h of treatment was reversed to control levels by PD98059, MEK inhibitor. SNAP also modulated the ERK1/2 phosphorylation in a time-dependent manner; an increase was observed up to 2h and thereafter the ERK1/2 phosphorylation was decreased. On the other hand, ODQ and KT5823 inhibitor of soluble guanylyl cyclase and protein kinase G respectively and MnTBAP, a scavenger of peroxynitrite, were unable to restore the SNAP-induced decreased expression of NPR-C protein and increased ERK1/2 phosphorylation to control levels. However, the decreased levels of p-ERK1/2 and Gi-proteins were restored to control levels by 8 bromo-cAMP. These results indicate that a temporal relationship follows between NO-induced decreased expression of NPR-C and Gia proteins. The decreased expression of NPR-C is mediated through cGMP-independent but MAP kinase-dependent pathway, whereas NO-induced decreased levels of cAMP may contribute to the decreased activation of MAP kinase and thereby decresed expression of Gi proteins.