Impact of stepwise annealing in the temperature ranges 300–750 K in vacuum chamber of scanning electron microscope on the cathodoluminescence of freshly introduced a-screw dislocations in low-ohmic GaN was investigated. Dislocation related luminescence (DRL) exhibits wide intense band at energy of about 3.12 eV at the room temperature and exceed an intensity of the near band edge emission. DRL intensity decreases with the temperature increase but remains detectable up to 450 K. Annealing at the temperatures up to 500 K does not change significantly structure of dislocations introduced at room temperature, while after the treatments at higher temperatures of up to 750 K the dislocations expand their length remaining in basal plane. The treatments however do not change DRL optical properties of the individual dislocations after cool down to room temperature.