Vascular Endothelial Growth Factor Acutely Reduces Calcium Influx Via Inhibition of the Ca2+ Channels in Rat Hippocampal Neurons

Vascular endothelial growth factor (VEGF) protects neurons against ischemic injury. An overload of intracellular calcium ions (Ca2+) caused by the excessive release of glutamate is widely considered to be one of the molecular mechanisms of ischemic neuronal death. In the present study, we investigated whether VEGF could modulate the activity of Ca2+ channels on the neuronal membrane. We used the Fluo-3 image method assisted by confocal laser scan microscopy to detect any Ca2+ influx in primary cultured hippocampal neurons. Whole-cell patch-clamp techniques were used to record the activity of the high-voltage-activated (HVA) Ca2+ currents in the CA1 pyramidal neurons of hippocampal slices that were freshly prepared from neonatal brains of rats. The results obtained from the Fluo-3 image experiments showed that VEGF pretreatment of cultured neurons at a final concentration of 50, 100, or 200 ng/ml acutely and dose dependently attenuated the Ca2+ influx induced by application of KCl (60 mM) or glutamate (50 mu M). This effect was blocked by SU1498, an antagonist of Flk-1 VEGF receptor. The influx of Ca2+ returned to basal levels after removal of VEGF. Furthermore, electrophysiological recording data showed that VEGF could acutely reduce the amplitudes of the HVA Ca2+ currents in a dose- and voltage-dependent manner. The HVA Ca2+ currents also returned to the levels of the control after removal of VEGF from the system. Taken together, the results obtained from the present study demonstrated that VEGF specifically reduced the influx of Ca2+ via the inhibitory activity of the HVA Ca2+ channels in hippo-campal neurons. (c) 2008 Wiley-Liss, Inc.