nNOS

Neuronal nitric oxide synthase (nNOS, NOS1) is a constitutively expressed nitric oxide synthase isoform that catalyzes nitric oxide (NO) production from L-arginine and functions as a major signaling enzyme in the central and peripheral nervous systems^[1][2]. Mechanistically, nNOS-derived NO participates in synaptic plasticity, long-term potentiation, and neuron-to-neuron communication through NO-dependent signaling pathways, thereby contributing to learning, memory, and neural network regulation^[2][3]. Beyond the nervous system, nNOS is also expressed in vascular tissues and contributes to cardiovascular homeostasis, vascular relaxation, and blood pressure regulation, indicating broader physiological functions than originally recognized^[4]. In disease-related contexts, dysregulated nNOS activity has been implicated in ischemic brain injury, neurodegenerative disorders, demyelination, and other conditions associated with excessive nitric oxide and reactive nitrogen species production^[3][5]. Compared with the related nitric oxide synthase isoforms, eNOS (NOS3) primarily regulates endothelial vascular function, whereas iNOS (NOS2) is inducible during inflammatory responses and generates substantially larger amounts of NO; in contrast, nNOS is calcium/calmodulin-dependent and mainly mediates physiological signaling processes^[1][2][4]. For experimental applications, selective nNOS inhibitors such as 7-nitroindazole (7-NI) have been widely used to investigate nNOS-specific functions and have demonstrated neuroprotective effects in animal models of ischemic and neurotoxic injury, making them valuable pharmacological tools for mechanistic studies^[6][7].