THE DEPOLARIZATION-INDUCED RELEASE OF [I-125] BDNF FROM BRAIN-TISSUE

The pattern of release of radioactive brain-derived neurotrophic facto r ([I-125]BDNF) from brain tissue was studied. Rat brain slices from c erebral cortex and synaptosomes from cerebral cortex and hippocampus w ere preloaded with [I-125]BDNF. Depolarising stimulation by veratridin e (final conc. 50 mu M) and high KCl (final conc. 45 mM) caused a shor t-term, greatly enhanced depolarisation-induced release of [I-125]BDNF during superfusion and batch protocol experiments. The results sugges ted that the evoked release was independent of the presence of extrace llular calcium ions, but dependent on intracellular calcium ion stores , since the intracellular calcium ion chelator BAPTA-AM, but not the e xtracellular chelator EGTA abolished the high-potassium-induced [I-125 ]BDNF release from synaptosomes. The release was blocked by tetrodotox in (1 mu M) when synaptosomes were stimulated by veratridine or potass ium chloride. Short time-fraction (30 s) superfusion experiments showe d that the [I-125]BDNF release from synaptosomes appeared in two tempo ral phases.