Nitric oxide (NO) radicals are produced during normal cellular function, after tissue injury, and in response to immune system activation during infection. The transformation of NO to peroxynitrite is essential for mediating some of its physiological and/or cytotoxic actions. As the expression of the adenosine A(1) receptor (A(1)AR) is regulated by oxidative stress, we evaluated the role of NO in the regulation of A(1)AR expression, a G protein-coupled receptor involved in cytoprotection in the central nervous system. Administration of the NO donor, S-nitrosylpenicillamine (SNAP), to pheochromocytoma 12 (PC12) cells increased A(1)AR protein in a time- and dose-dependent manner, with maximal induction observed with 20 mu M SNAP at 24 h. The response to SNAP was attenuated by the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3 oxide (C-PTIO), and by the inhibition of nuclear factor-kappa B (NF-kappa B), implicating this transcription factor in the regulatory process. In addition SNAP also increased the degradation of Inhibitory kappa B-alpha (I kappa B-alpha), a marker of NF-kappa B activation. Furthermore, the induction of inducible nitric oxide synthase (iNOS) by lipopolysaccharide increased A(1)AR in PC12 cells and in mice, whereas the inhibition of NOS activity suppressed this response. We conclude that NO, via the activation of NF-kappa B, serves as an endogenous regulator of A(1)AR, and speculate that the induction of the A(1)AR could counteract the cytotoxicity of NO.