There can be three definitions of a base: Arrhenius base, Lewis base or Bronsted-Lowry base. Isoquinoline acts specifically as a Bronsted-Lowry base, which is a proton acceptor. Also, it acts as an Arrhenius base because it produces OH- ions after the reaction. The net ionic equation is:
C₉H₇N (aq) + H₂O ---> C₉H₇NH⁺ (aq) + OH⁻ (aq)