The present invention features quinolones, tetrahydroquinolines, and related compounds that inhibit nitric oxide synthase (NOS), particularly those that selectively inhibit neuronal nitric oxide synthase (nNOS) in preference to other NOS isoforms. The NOS inhibitors of the invention, alone or in combination with other pharmaceutically active agents, can be used for treating or preventing various medical conditions.本發明提供喹諾酮、四氫喹啉及其相關化合物,其抑制一氧化氮合成酶(NOS),尤其相較於其他NOS同功異構物,可選擇性抑制神經元性一氧化氮合成酶(nNOS)。本發明之NOS抑制劑,當單獨或與其他醫藥上的活性試劑結合,可用於治療或預防各種醫學症狀。