Non-thermal plasmas operating at high pressure attract increasing attention for a variety of applications as an alternative to conventional chemical processes. In this study, an atmospheric pressure direct current non-self-sustained discharge in nitrogen is investigated as a source of non-thermal plasma capable of operating in a glow regime. The discharge is sustained between an internal source of ionization and a metal or liquid electrode and studied by electrical diagnostics as well as by spectroscopy methods. The work is focused on the determination of the discharge properties including vibrational and gas temperature. The effect of the liquid electrode on the discharge properties is studied and analyzed. The mechanisms of the discharge sustaining and pathways of nitrogen state excitation are discussed.