Direct effect of electrical stimulation on induction of brain-derived neurotrophic factor from cultured retinal muller cells

PURPOSE. To investigate the direct effect of electrical stimulation (ES) on the induction of brain-derived neurotrophic factor (BDNF) from cultured retinal Muller cells. METHODS. Muller cells were isolated from rat retinas. ES was applied to passage 1 Muller cells with biphasic pulses (duration, 1 ms; frequency, 20 Hz; current, 10 mA) for 30 minutes. The changes in gene expression after ES were analyzed with microarrays. The mRNA and protein levels of BDNF were determined at each time point after ES by RT-PCR and ELISA, respectively. RT-PCR was also performed at 3 hours after ES of Muller cells that had been exposed to 1 mu M nifedipine, a blocker of L-type voltage-dependent calcium channels (L-VDCCs). RESULTS. Microarray analyses showed an upregulation of 245 genes, including BDNF. The mRNA level of BDNF increased significantly (P < 0.05; by similar to 1.2-fold over that of the control) at 2 and 3 hours after ES. The intracellular protein level was upregulated significantly ( by similar to 1.4-fold) at 6 hours after ES, whereas the extracellular level did not change at any time point. The total protein level of BDNF increased significantly (similar to 1.3-fold) at 6 hours after ES. The increase in the mRNA level of BDNF was fully suppressed by exposure of the Muller cells to nifedipine. CONCLUSIONS. These results demonstrate that ES directly upregulates the transcriptional induction of BDNF through L-VDCCs in cultured Muller cells. The ES of Muller cells may be used to supply endogenous BDNF to the retina.