Used in neuroscience and endocrinology research to measure hydroxynorepinephrine levels in rat biological samples such as plasma, serum, or tissue homogenates. Helps in studying the regulation of catecholamine synthesis and adrenal function in rodent models. Commonly applied in experiments related to stress response, autonomic nervous system activity, and neurodegenerative disorders. Provides a reliable, sensitive method for quantifying changes in hydroxynorepinephrine due to pharmacological treatments or genetic modifications in rat studies.