The depolarisation-induced release of [I-125]BDNF from brain tissue

The pattern of release of radioactive brain-derived neurotrophic factor ([I-125]BDNF) from brain tissue was studied. Rat brain slices from cerebral cortex and synaptosomes from cerebral cortex and hippocampus were preloaded with [I-125]BDNF. Depolarising stimulation by veratridine (final conc. 50 mu M) and high KCl (final conc. 45 mM) caused a short-term, greatly enhanced depolarisation-induced release of [I-125]BDNF during superfusion and batch protocol experiments. The results suggested that the evoked release was independent of the presence of extracellular calcium ions, but dependent on intracellular calcium ion stores, since the intracellular calcium ion chelator BAPTA-AM, but not the extracellular chelator EGTA abolished the high-potassium-induced [I-125]BDNF release from synaptosomes. The release was blocked by tetrodotoxin (1 mu M) when synaptosomes were stimulated by veratridine or potassium chloride. Short time-fraction (30 s) superfusion experiments showed that the [I-125]BDNF release from synaptosomes appeared in two temporal phases.